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735 <body class=
"article">
737 <h1>My First Contribution to the Git Project
</h1>
738 <span id=
"revdate">2024-
07-
16</span>
742 <h2 id=
"summary">Summary
</h2>
743 <div class=
"sectionbody">
744 <div class=
"paragraph"><p>This is a tutorial demonstrating the end-to-end workflow of creating a change to
745 the Git tree, sending it for review, and making changes based on comments.
</p></div>
747 <h3 id=
"prerequisites">Prerequisites
</h3>
748 <div class=
"paragraph"><p>This tutorial assumes you
’re already fairly familiar with using Git to manage
749 source code. The Git workflow steps will largely remain unexplained.
</p></div>
752 <h3 id=
"related-reading">Related Reading
</h3>
753 <div class=
"paragraph"><p>This tutorial aims to summarize the following documents, but the reader may find
754 useful additional context:
</p></div>
755 <div class=
"ulist"><ul>
758 <code>Documentation/SubmittingPatches
</code>
763 <code>Documentation/howto/new-command.txt
</code>
769 <h3 id=
"getting-help">Getting Help
</h3>
770 <div class=
"paragraph"><p>If you get stuck, you can seek help in the following places.
</p></div>
772 <h4 id=
"_a_href_mailto_git_vger_kernel_org_git_vger_kernel_org_a"><a href=
"mailto:git@vger.kernel.org">git@vger.kernel.org
</a></h4>
773 <div class=
"paragraph"><p>This is the main Git project mailing list where code reviews, version
774 announcements, design discussions, and more take place. Those interested in
775 contributing are welcome to post questions here. The Git list requires
776 plain-text-only emails and prefers inline and bottom-posting when replying to
777 mail; you will be CC
’d in all replies to you. Optionally, you can subscribe to
778 the list by sending an email to
<git+
<a href=
"mailto:subscribe@vger.kernel.org">subscribe@vger.kernel.org
</a>>
779 (see
<a href=
"https://subspace.kernel.org/subscribing.html">https://subspace.kernel.org/subscribing.html
</a> for details).
780 The
<a href=
"https://lore.kernel.org/git">archive
</a> of this mailing list is
781 available to view in a browser.
</p></div>
784 <h4 id=
"_a_href_https_groups_google_com_forum_forum_git_mentoring_git_mentoring_googlegroups_com_a"><a href=
"https://groups.google.com/forum/#!forum/git-mentoring">git-mentoring@googlegroups.com
</a></h4>
785 <div class=
"paragraph"><p>This mailing list is targeted to new contributors and was created as a place to
786 post questions and receive answers outside of the public eye of the main list.
787 Veteran contributors who are especially interested in helping mentor newcomers
788 are present on the list. In order to avoid search indexers, group membership is
789 required to view messages; anyone can join and no approval is required.
</p></div>
792 <h4 id=
"_a_href_https_web_libera_chat_git_devel_git_devel_a_on_libera_chat"><a href=
"https://web.libera.chat/#git-devel">#git-devel
</a> on Libera Chat
</h4>
793 <div class=
"paragraph"><p>This IRC channel is for conversations between Git contributors. If someone is
794 currently online and knows the answer to your question, you can receive help
795 in real time. Otherwise, you can read the
796 <a href=
"https://colabti.org/irclogger/irclogger_logs/git-devel">scrollback
</a> to see
797 whether someone answered you. IRC does not allow offline private messaging, so
798 if you try to private message someone and then log out of IRC, they cannot
799 respond to you. It
’s better to ask your questions in the channel so that you
800 can be answered if you disconnect and so that others can learn from the
801 conversation.
</p></div>
807 <h2 id=
"getting-started">Getting Started
</h2>
808 <div class=
"sectionbody">
810 <h3 id=
"cloning">Clone the Git Repository
</h3>
811 <div class=
"paragraph"><p>Git is mirrored in a number of locations. Clone the repository from one of them;
812 <a href=
"https://git-scm.com/downloads">https://git-scm.com/downloads
</a> suggests one of the best places to clone from is
813 the mirror on GitHub.
</p></div>
814 <div class=
"listingblock">
815 <div class=
"content">
816 <pre><code>$ git clone https://github.com/git/git git
817 $ cd git
</code></pre>
821 <h3 id=
"dependencies">Installing Dependencies
</h3>
822 <div class=
"paragraph"><p>To build Git from source, you need to have a handful of dependencies installed
823 on your system. For a hint of what
’s needed, you can take a look at
824 <code>INSTALL
</code>, paying close attention to the section about Git
’s dependencies on
825 external programs and libraries. That document mentions a way to
"test-drive"
826 our freshly built Git without installing; that
’s the method we
’ll be using in
827 this tutorial.
</p></div>
828 <div class=
"paragraph"><p>Make sure that your environment has everything you need by building your brand
829 new clone of Git from the above step:
</p></div>
830 <div class=
"listingblock">
831 <div class=
"content">
832 <pre><code>$ make
</code></pre>
834 <div class=
"admonitionblock">
837 <div class=
"title">Note
</div>
839 <td class=
"content">The Git build is parallelizable.
<code>-j#
</code> is not included above but you can
840 use it as you prefer, here and elsewhere.
</td>
845 <h3 id=
"identify-problem">Identify Problem to Solve
</h3>
846 <div class=
"paragraph"><p>In this tutorial, we will add a new command,
<code>git psuh
</code>, short for
“Pony Saying
847 ‘Um, Hello
”’ - a feature which has gone unimplemented despite a high frequency
848 of invocation during users' typical daily workflow.
</p></div>
849 <div class=
"paragraph"><p>(We
’ve seen some other effort in this space with the implementation of popular
850 commands such as
<code>sl
</code>.)
</p></div>
853 <h3 id=
"setup-workspace">Set Up Your Workspace
</h3>
854 <div class=
"paragraph"><p>Let
’s start by making a development branch to work on our changes. Per
855 <code>Documentation/SubmittingPatches
</code>, since a brand new command is a new feature,
856 it
’s fine to base your work on
<code>master
</code>. However, in the future for bugfixes,
857 etc., you should check that document and base it on the appropriate branch.
</p></div>
858 <div class=
"paragraph"><p>For the purposes of this document, we will base all our work on the
<code>master
</code>
859 branch of the upstream project. Create the
<code>psuh
</code> branch you will use for
860 development like so:
</p></div>
861 <div class=
"listingblock">
862 <div class=
"content">
863 <pre><code>$ git checkout -b psuh origin/master
</code></pre>
865 <div class=
"paragraph"><p>We
’ll make a number of commits here in order to demonstrate how to send a topic
866 with multiple patches up for review simultaneously.
</p></div>
871 <h2 id=
"code-it-up">Code It Up!
</h2>
872 <div class=
"sectionbody">
873 <div class=
"admonitionblock">
876 <div class=
"title">Note
</div>
878 <td class=
"content">A reference implementation can be found at
879 <a href=
"https://github.com/nasamuffin/git/tree/psuh">https://github.com/nasamuffin/git/tree/psuh
</a>.
</td>
883 <h3 id=
"add-new-command">Adding a New Command
</h3>
884 <div class=
"paragraph"><p>Lots of the subcommands are written as builtins, which means they are
885 implemented in C and compiled into the main
<code>git
</code> executable. Implementing the
886 very simple
<code>psuh
</code> command as a built-in will demonstrate the structure of the
887 codebase, the internal API, and the process of working together as a contributor
888 with the reviewers and maintainer to integrate this change into the system.
</p></div>
889 <div class=
"paragraph"><p>Built-in subcommands are typically implemented in a function named
"cmd_"
890 followed by the name of the subcommand, in a source file named after the
891 subcommand and contained within
<code>builtin/
</code>. So it makes sense to implement your
892 command in
<code>builtin/psuh.c
</code>. Create that file, and within it, write the entry
893 point for your command in a function matching the style and signature:
</p></div>
894 <div class=
"listingblock">
895 <div class=
"content">
896 <pre><code>int cmd_psuh(int argc, const char **argv, const char *prefix)
</code></pre>
898 <div class=
"paragraph"><p>We
’ll also need to add the declaration of psuh; open up
<code>builtin.h
</code>, find the
899 declaration for
<code>cmd_pull
</code>, and add a new line for
<code>psuh
</code> immediately before it,
900 in order to keep the declarations alphabetically sorted:
</p></div>
901 <div class=
"listingblock">
902 <div class=
"content">
903 <pre><code>int cmd_psuh(int argc, const char **argv, const char *prefix);
</code></pre>
905 <div class=
"paragraph"><p>Be sure to
<code>#include
"builtin.h"</code> in your
<code>psuh.c
</code>. You
’ll also need to
906 <code>#include
"gettext.h"</code> to use functions related to printing output text.
</p></div>
907 <div class=
"paragraph"><p>Go ahead and add some throwaway printf to the
<code>cmd_psuh
</code> function. This is a
908 decent starting point as we can now add build rules and register the command.
</p></div>
909 <div class=
"admonitionblock">
912 <div class=
"title">Note
</div>
914 <td class=
"content">Your throwaway text, as well as much of the text you will be adding over
915 the course of this tutorial, is user-facing. That means it needs to be
916 localizable. Take a look at
<code>po/README
</code> under
"Marking strings for translation".
917 Throughout the tutorial, we will mark strings for translation as necessary; you
918 should also do so when writing your user-facing commands in the future.
</td>
921 <div class=
"listingblock">
922 <div class=
"content">
923 <pre><code>int cmd_psuh(int argc, const char **argv, const char *prefix)
925 printf(_(
"Pony saying hello goes here.\n"));
929 <div class=
"paragraph"><p>Let
’s try to build it. Open
<code>Makefile
</code>, find where
<code>builtin/pull.o
</code> is added
930 to
<code>BUILTIN_OBJS
</code>, and add
<code>builtin/psuh.o
</code> in the same way next to it in
931 alphabetical order. Once you
’ve done so, move to the top-level directory and
932 build simply with
<code>make
</code>. Also add the
<code>DEVELOPER=
1</code> variable to turn on
933 some additional warnings:
</p></div>
934 <div class=
"listingblock">
935 <div class=
"content">
936 <pre><code>$ echo DEVELOPER=
1 >config.mak
939 <div class=
"admonitionblock">
942 <div class=
"title">Note
</div>
944 <td class=
"content">When you are developing the Git project, it
’s preferred that you use the
945 <code>DEVELOPER
</code> flag; if there
’s some reason it doesn
’t work for you, you can turn
946 it off, but it
’s a good idea to mention the problem to the mailing list.
</td>
949 <div class=
"paragraph"><p>Great, now your new command builds happily on its own. But nobody invokes it.
950 Let
’s change that.
</p></div>
951 <div class=
"paragraph"><p>The list of commands lives in
<code>git.c
</code>. We can register a new command by adding
952 a
<code>cmd_struct
</code> to the
<code>commands[]
</code> array.
<code>struct cmd_struct
</code> takes a string
953 with the command name, a function pointer to the command implementation, and a
954 setup option flag. For now, let
’s keep mimicking
<code>push
</code>. Find the line where
955 <code>cmd_push
</code> is registered, copy it, and modify it for
<code>cmd_psuh
</code>, placing the new
956 line in alphabetical order (immediately before
<code>cmd_pull
</code>).
</p></div>
957 <div class=
"paragraph"><p>The options are documented in
<code>builtin.h
</code> under
"Adding a new built-in." Since
958 we hope to print some data about the user
’s current workspace context later,
959 we need a Git directory, so choose
<code>RUN_SETUP
</code> as your only option.
</p></div>
960 <div class=
"paragraph"><p>Go ahead and build again. You should see a clean build, so let
’s kick the tires
961 and see if it works. There
’s a binary you can use to test with in the
962 <code>bin-wrappers
</code> directory.
</p></div>
963 <div class=
"listingblock">
964 <div class=
"content">
965 <pre><code>$ ./bin-wrappers/git psuh
</code></pre>
967 <div class=
"paragraph"><p>Check it out! You
’ve got a command! Nice work! Let
’s commit this.
</p></div>
968 <div class=
"paragraph"><p><code>git status
</code> reveals modified
<code>Makefile
</code>,
<code>builtin.h
</code>, and
<code>git.c
</code> as well as
969 untracked
<code>builtin/psuh.c
</code> and
<code>git-psuh
</code>. First, let
’s take care of the binary,
970 which should be ignored. Open
<code>.gitignore
</code> in your editor, find
<code>/git-pull
</code>, and
971 add an entry for your new command in alphabetical order:
</p></div>
972 <div class=
"listingblock">
973 <div class=
"content">
983 <div class=
"paragraph"><p>Checking
<code>git status
</code> again should show that
<code>git-psuh
</code> has been removed from
984 the untracked list and
<code>.gitignore
</code> has been added to the modified list. Now we
985 can stage and commit:
</p></div>
986 <div class=
"listingblock">
987 <div class=
"content">
988 <pre><code>$ git add Makefile builtin.h builtin/psuh.c git.c .gitignore
989 $ git commit -s
</code></pre>
991 <div class=
"paragraph"><p>You will be presented with your editor in order to write a commit message. Start
992 the commit with a
50-column or less subject line, including the name of the
993 component you
’re working on, followed by a blank line (always required) and then
994 the body of your commit message, which should provide the bulk of the context.
995 Remember to be explicit and provide the
"Why" of your change, especially if it
996 couldn
’t easily be understood from your diff. When editing your commit message,
997 don
’t remove the
<code>Signed-off-by
</code> trailer which was added by
<code>-s
</code> above.
</p></div>
998 <div class=
"listingblock">
999 <div class=
"content">
1000 <pre><code>psuh: add a built-in by popular demand
1002 Internal metrics indicate this is a command many users expect to be
1003 present. So here's an implementation to help drive customer
1004 satisfaction and engagement: a pony which doubtfully greets the user,
1005 or, a Pony Saying
"Um, Hello" (PSUH).
1007 This commit message is intentionally formatted to
72 columns per line,
1008 starts with a single line as
"commit message subject" that is written as
1009 if to command the codebase to do something (add this, teach a command
1010 that). The body of the message is designed to add information about the
1011 commit that is not readily deduced from reading the associated diff,
1012 such as answering the question
"why?".
1014 Signed-off-by: A U Thor
<author@example.com
></code></pre>
1016 <div class=
"paragraph"><p>Go ahead and inspect your new commit with
<code>git show
</code>.
"psuh:" indicates you
1017 have modified mainly the
<code>psuh
</code> command. The subject line gives readers an idea
1018 of what you
’ve changed. The sign-off line (
<code>-s
</code>) indicates that you agree to
1019 the Developer
’s Certificate of Origin
1.1 (see the
1020 <code>Documentation/SubmittingPatches
</code> [[dco]] header).
</p></div>
1021 <div class=
"paragraph"><p>For the remainder of the tutorial, the subject line only will be listed for the
1022 sake of brevity. However, fully-fleshed example commit messages are available
1023 on the reference implementation linked at the top of this document.
</p></div>
1026 <h3 id=
"implementation">Implementation
</h3>
1027 <div class=
"paragraph"><p>It
’s probably useful to do at least something besides printing out a string.
1028 Let
’s start by having a look at everything we get.
</p></div>
1029 <div class=
"paragraph"><p>Modify your
<code>cmd_psuh
</code> implementation to dump the args you
’re passed, keeping
1030 existing
<code>printf()
</code> calls in place:
</p></div>
1031 <div class=
"listingblock">
1032 <div class=
"content">
1037 printf(Q_(
"Your args (there is %d):\n",
1038 "Your args (there are %d):\n",
1041 for (i =
0; i
< argc; i++)
1042 printf(
"%d: %s\n", i, argv[i]);
1044 printf(_(
"Your current working directory:\n<top-level>%s%s\n"),
1045 prefix ?
"/" :
"", prefix ? prefix :
"");
</code></pre>
1047 <div class=
"paragraph"><p>Build and try it. As you may expect, there
’s pretty much just whatever we give
1048 on the command line, including the name of our command. (If
<code>prefix
</code> is empty
1049 for you, try
<code>cd Documentation/
&& ../bin-wrappers/git psuh
</code>). That
’s not so
1050 helpful. So what other context can we get?
</p></div>
1051 <div class=
"paragraph"><p>Add a line to
<code>#include
"config.h"</code>. Then, add the following bits to the
1052 function body:
</p></div>
1053 <div class=
"listingblock">
1054 <div class=
"content">
1055 <pre><code> const char *cfg_name;
1059 git_config(git_default_config, NULL);
1060 if (git_config_get_string_tmp(
"user.name",
&cfg_name)
> 0)
1061 printf(_(
"No name is found in config\n"));
1063 printf(_(
"Your name: %s\n"), cfg_name);
</code></pre>
1065 <div class=
"paragraph"><p><code>git_config()
</code> will grab the configuration from config files known to Git and
1066 apply standard precedence rules.
<code>git_config_get_string_tmp()
</code> will look up
1067 a specific key (
"user.name") and give you the value. There are a number of
1068 single-key lookup functions like this one; you can see them all (and more info
1069 about how to use
<code>git_config()
</code>) in
<code>Documentation/technical/api-config.txt
</code>.
</p></div>
1070 <div class=
"paragraph"><p>You should see that the name printed matches the one you see when you run:
</p></div>
1071 <div class=
"listingblock">
1072 <div class=
"content">
1073 <pre><code>$ git config --get user.name
</code></pre>
1075 <div class=
"paragraph"><p>Great! Now we know how to check for values in the Git config. Let
’s commit this
1076 too, so we don
’t lose our progress.
</p></div>
1077 <div class=
"listingblock">
1078 <div class=
"content">
1079 <pre><code>$ git add builtin/psuh.c
1080 $ git commit -sm
"psuh: show parameters & config opts"</code></pre>
1082 <div class=
"admonitionblock">
1085 <div class=
"title">Note
</div>
1087 <td class=
"content">Again, the above is for sake of brevity in this tutorial. In a real change
1088 you should not use
<code>-m
</code> but instead use the editor to write a meaningful
1092 <div class=
"paragraph"><p>Still, it
’d be nice to know what the user
’s working context is like. Let
’s see
1093 if we can print the name of the user
’s current branch. We can mimic the
1094 <code>git status
</code> implementation; the printer is located in
<code>wt-status.c
</code> and we can
1095 see that the branch is held in a
<code>struct wt_status
</code>.
</p></div>
1096 <div class=
"paragraph"><p><code>wt_status_print()
</code> gets invoked by
<code>cmd_status()
</code> in
<code>builtin/commit.c
</code>.
1097 Looking at that implementation we see the status config being populated like so:
</p></div>
1098 <div class=
"listingblock">
1099 <div class=
"content">
1100 <pre><code>status_init_config(
&s, git_status_config);
</code></pre>
1102 <div class=
"paragraph"><p>But as we drill down, we can find that
<code>status_init_config()
</code> wraps a call
1103 to
<code>git_config()
</code>. Let
’s modify the code we wrote in the previous commit.
</p></div>
1104 <div class=
"paragraph"><p>Be sure to include the header to allow you to use
<code>struct wt_status
</code>:
</p></div>
1105 <div class=
"listingblock">
1106 <div class=
"content">
1107 <pre><code>#include
"wt-status.h"</code></pre>
1109 <div class=
"paragraph"><p>Then modify your
<code>cmd_psuh
</code> implementation to declare your
<code>struct wt_status
</code>,
1110 prepare it, and print its contents:
</p></div>
1111 <div class=
"listingblock">
1112 <div class=
"content">
1113 <pre><code> struct wt_status status;
1117 wt_status_prepare(the_repository,
&status);
1118 git_config(git_default_config,
&status);
1122 printf(_(
"Your current branch: %s\n"), status.branch);
</code></pre>
1124 <div class=
"paragraph"><p>Run it again. Check it out - here
’s the (verbose) name of your current branch!
</p></div>
1125 <div class=
"paragraph"><p>Let
’s commit this as well.
</p></div>
1126 <div class=
"listingblock">
1127 <div class=
"content">
1128 <pre><code>$ git add builtin/psuh.c
1129 $ git commit -sm
"psuh: print the current branch"</code></pre>
1131 <div class=
"paragraph"><p>Now let
’s see if we can get some info about a specific commit.
</p></div>
1132 <div class=
"paragraph"><p>Luckily, there are some helpers for us here.
<code>commit.h
</code> has a function called
1133 <code>lookup_commit_reference_by_name
</code> to which we can simply provide a hardcoded
1134 string;
<code>pretty.h
</code> has an extremely handy
<code>pp_commit_easy()
</code> call which doesn
’t
1135 require a full format object to be passed.
</p></div>
1136 <div class=
"paragraph"><p>Add the following includes:
</p></div>
1137 <div class=
"listingblock">
1138 <div class=
"content">
1139 <pre><code>#include
"commit.h"
1140 #include
"pretty.h"</code></pre>
1142 <div class=
"paragraph"><p>Then, add the following lines within your implementation of
<code>cmd_psuh()
</code> near
1143 the declarations and the logic, respectively.
</p></div>
1144 <div class=
"listingblock">
1145 <div class=
"content">
1146 <pre><code> struct commit *c = NULL;
1147 struct strbuf commitline = STRBUF_INIT;
1151 c = lookup_commit_reference_by_name(
"origin/master");
1154 pp_commit_easy(CMIT_FMT_ONELINE, c,
&commitline);
1155 printf(_(
"Current commit: %s\n"), commitline.buf);
1158 <div class=
"paragraph"><p>The
<code>struct strbuf
</code> provides some safety belts to your basic
<code>char*
</code>, one of
1159 which is a length member to prevent buffer overruns. It needs to be initialized
1160 nicely with
<code>STRBUF_INIT
</code>. Keep it in mind when you need to pass around
<code>char*
</code>.
</p></div>
1161 <div class=
"paragraph"><p><code>lookup_commit_reference_by_name
</code> resolves the name you pass it, so you can play
1162 with the value there and see what kind of things you can come up with.
</p></div>
1163 <div class=
"paragraph"><p><code>pp_commit_easy
</code> is a convenience wrapper in
<code>pretty.h
</code> that takes a single
1164 format enum shorthand, rather than an entire format struct. It then
1165 pretty-prints the commit according to that shorthand. These are similar to the
1166 formats available with
<code>--pretty=FOO
</code> in many Git commands.
</p></div>
1167 <div class=
"paragraph"><p>Build it and run, and if you
’re using the same name in the example, you should
1168 see the subject line of the most recent commit in
<code>origin/master
</code> that you know
1169 about. Neat! Let
’s commit that as well.
</p></div>
1170 <div class=
"listingblock">
1171 <div class=
"content">
1172 <pre><code>$ git add builtin/psuh.c
1173 $ git commit -sm
"psuh: display the top of origin/master"</code></pre>
1177 <h3 id=
"add-documentation">Adding Documentation
</h3>
1178 <div class=
"paragraph"><p>Awesome! You
’ve got a fantastic new command that you
’re ready to share with the
1179 community. But hang on just a minute - this isn
’t very user-friendly. Run the
1180 following:
</p></div>
1181 <div class=
"listingblock">
1182 <div class=
"content">
1183 <pre><code>$ ./bin-wrappers/git help psuh
</code></pre>
1185 <div class=
"paragraph"><p>Your new command is undocumented! Let
’s fix that.
</p></div>
1186 <div class=
"paragraph"><p>Take a look at
<code>Documentation/git-*.txt
</code>. These are the manpages for the
1187 subcommands that Git knows about. You can open these up and take a look to get
1188 acquainted with the format, but then go ahead and make a new file
1189 <code>Documentation/git-psuh.txt
</code>. Like with most of the documentation in the Git
1190 project, help pages are written with AsciiDoc (see CodingGuidelines,
"Writing
1191 Documentation" section). Use the following template to fill out your own
1193 <div class=
"listingblock">
1194 <div class=
"content">
1195 <pre><code>git-psuh(
1)
1200 git-psuh - Delight users' typo with a shy horse
1206 'git-psuh [
<arg
>...]'
1222 Part of the linkgit:git[
1] suite
</code></pre>
1224 <div class=
"paragraph"><p>The most important pieces of this to note are the file header, underlined by =,
1225 the NAME section, and the SYNOPSIS, which would normally contain the grammar if
1226 your command took arguments. Try to use well-established manpage headers so your
1227 documentation is consistent with other Git and UNIX manpages; this makes life
1228 easier for your user, who can skip to the section they know contains the
1229 information they need.
</p></div>
1230 <div class=
"admonitionblock">
1233 <div class=
"title">Note
</div>
1235 <td class=
"content">Before trying to build the docs, make sure you have the package
<code>asciidoc
</code>
1239 <div class=
"paragraph"><p>Now that you
’ve written your manpage, you
’ll need to build it explicitly. We
1240 convert your AsciiDoc to troff which is man-readable like so:
</p></div>
1241 <div class=
"listingblock">
1242 <div class=
"content">
1243 <pre><code>$ make all doc
1244 $ man Documentation/git-psuh
.1</code></pre>
1246 <div class=
"paragraph"><p>or
</p></div>
1247 <div class=
"listingblock">
1248 <div class=
"content">
1249 <pre><code>$ make -C Documentation/ git-psuh
.1
1250 $ man Documentation/git-psuh
.1</code></pre>
1252 <div class=
"paragraph"><p>While this isn
’t as satisfying as running through
<code>git help
</code>, you can at least
1253 check that your help page looks right.
</p></div>
1254 <div class=
"paragraph"><p>You can also check that the documentation coverage is good (that is, the project
1255 sees that your command has been implemented as well as documented) by running
1256 <code>make check-docs
</code> from the top-level.
</p></div>
1257 <div class=
"paragraph"><p>Go ahead and commit your new documentation change.
</p></div>
1260 <h3 id=
"add-usage">Adding Usage Text
</h3>
1261 <div class=
"paragraph"><p>Try and run
<code>./bin-wrappers/git psuh -h
</code>. Your command should crash at the end.
1262 That
’s because
<code>-h
</code> is a special case which your command should handle by
1263 printing usage.
</p></div>
1264 <div class=
"paragraph"><p>Take a look at
<code>Documentation/technical/api-parse-options.txt
</code>. This is a handy
1265 tool for pulling out options you need to be able to handle, and it takes a
1266 usage string.
</p></div>
1267 <div class=
"paragraph"><p>In order to use it, we
’ll need to prepare a NULL-terminated array of usage
1268 strings and a
<code>builtin_psuh_options
</code> array.
</p></div>
1269 <div class=
"paragraph"><p>Add a line to
<code>#include
"parse-options.h"</code>.
</p></div>
1270 <div class=
"paragraph"><p>At global scope, add your array of usage strings:
</p></div>
1271 <div class=
"listingblock">
1272 <div class=
"content">
1273 <pre><code>static const char * const psuh_usage[] = {
1274 N_(
"git psuh [<arg>...]"),
1278 <div class=
"paragraph"><p>Then, within your
<code>cmd_psuh()
</code> implementation, we can declare and populate our
1279 <code>option
</code> struct. Ours is pretty boring but you can add more to it if you want to
1280 explore
<code>parse_options()
</code> in more detail:
</p></div>
1281 <div class=
"listingblock">
1282 <div class=
"content">
1283 <pre><code> struct option options[] = {
1287 <div class=
"paragraph"><p>Finally, before you print your args and prefix, add the call to
1288 <code>parse-options()
</code>:
</p></div>
1289 <div class=
"listingblock">
1290 <div class=
"content">
1291 <pre><code> argc = parse_options(argc, argv, prefix, options, psuh_usage,
0);
</code></pre>
1293 <div class=
"paragraph"><p>This call will modify your
<code>argv
</code> parameter. It will strip the options you
1294 specified in
<code>options
</code> from
<code>argv
</code> and the locations pointed to from
<code>options
</code>
1295 entries will be updated. Be sure to replace your
<code>argc
</code> with the result from
1296 <code>parse_options()
</code>, or you will be confused if you try to parse
<code>argv
</code> later.
</p></div>
1297 <div class=
"paragraph"><p>It
’s worth noting the special argument
<code>--
</code>. As you may be aware, many Unix
1298 commands use
<code>--
</code> to indicate
"end of named parameters" - all parameters after
1299 the
<code>--
</code> are interpreted merely as positional arguments. (This can be handy if
1300 you want to pass as a parameter something which would usually be interpreted as
1301 a flag.)
<code>parse_options()
</code> will terminate parsing when it reaches
<code>--
</code> and give
1302 you the rest of the options afterwards, untouched.
</p></div>
1303 <div class=
"paragraph"><p>Now that you have a usage hint, you can teach Git how to show it in the general
1304 command list shown by
<code>git help git
</code> or
<code>git help -a
</code>, which is generated from
1305 <code>command-list.txt
</code>. Find the line for
<em>git-pull
</em> so you can add your
<em>git-psuh
</em>
1306 line above it in alphabetical order. Now, we can add some attributes about the
1307 command which impacts where it shows up in the aforementioned help commands. The
1308 top of
<code>command-list.txt
</code> shares some information about what each attribute
1309 means; in those help pages, the commands are sorted according to these
1310 attributes.
<code>git psuh
</code> is user-facing, or porcelain - so we will mark it as
1311 "mainporcelain". For
"mainporcelain" commands, the comments at the top of
1312 <code>command-list.txt
</code> indicate we can also optionally add an attribute from another
1313 list; since
<code>git psuh
</code> shows some information about the user
’s workspace but
1314 doesn
’t modify anything, let
’s mark it as
"info". Make sure to keep your
1315 attributes in the same style as the rest of
<code>command-list.txt
</code> using spaces to
1316 align and delineate them:
</p></div>
1317 <div class=
"listingblock">
1318 <div class=
"content">
1319 <pre><code>git-prune-packed plumbingmanipulators
1320 git-psuh mainporcelain info
1321 git-pull mainporcelain remote
1322 git-push mainporcelain remote
</code></pre>
1324 <div class=
"paragraph"><p>Build again. Now, when you run with
<code>-h
</code>, you should see your usage printed and
1325 your command terminated before anything else interesting happens. Great!
</p></div>
1326 <div class=
"paragraph"><p>Go ahead and commit this one, too.
</p></div>
1331 <h2 id=
"testing">Testing
</h2>
1332 <div class=
"sectionbody">
1333 <div class=
"paragraph"><p>It
’s important to test your code - even for a little toy command like this one.
1334 Moreover, your patch won
’t be accepted into the Git tree without tests. Your
1335 tests should:
</p></div>
1336 <div class=
"ulist"><ul>
1339 Illustrate the current behavior of the feature
1344 Prove the current behavior matches the expected behavior
1349 Ensure the externally-visible behavior isn
’t broken in later changes
1353 <div class=
"paragraph"><p>So let
’s write some tests.
</p></div>
1354 <div class=
"paragraph"><p>Related reading:
<code>t/README
</code></p></div>
1356 <h3 id=
"overview-test-structure">Overview of Testing Structure
</h3>
1357 <div class=
"paragraph"><p>The tests in Git live in
<code>t/
</code> and are named with a
4-digit decimal number using
1358 the schema shown in the Naming Tests section of
<code>t/README
</code>.
</p></div>
1361 <h3 id=
"write-new-test">Writing Your Test
</h3>
1362 <div class=
"paragraph"><p>Since this a toy command, let
’s go ahead and name the test with t9999. However,
1363 as many of the family/subcmd combinations are full, best practice seems to be
1364 to find a command close enough to the one you
’ve added and share its naming
1366 <div class=
"paragraph"><p>Create a new file
<code>t/t9999-psuh-tutorial.sh
</code>. Begin with the header as so (see
1367 "Writing Tests" and
"Source <em>test-lib.sh</em>" in
<code>t/README
</code>):
</p></div>
1368 <div class=
"listingblock">
1369 <div class=
"content">
1370 <pre><code>#!/bin/sh
1372 test_description='git-psuh test
1374 This test runs git-psuh and makes sure it does not crash.'
1376 . ./test-lib.sh
</code></pre>
1378 <div class=
"paragraph"><p>Tests are framed inside of a
<code>test_expect_success
</code> in order to output TAP
1379 formatted results. Let
’s make sure that
<code>git psuh
</code> doesn
’t exit poorly and does
1380 mention the right animal somewhere:
</p></div>
1381 <div class=
"listingblock">
1382 <div class=
"content">
1383 <pre><code>test_expect_success 'runs correctly with no args and good output' '
1384 git psuh
>actual
&&
1388 <div class=
"paragraph"><p>Indicate that you
’ve run everything you wanted by adding the following at the
1389 bottom of your script:
</p></div>
1390 <div class=
"listingblock">
1391 <div class=
"content">
1392 <pre><code>test_done
</code></pre>
1394 <div class=
"paragraph"><p>Make sure you mark your test script executable:
</p></div>
1395 <div class=
"listingblock">
1396 <div class=
"content">
1397 <pre><code>$ chmod +x t/t9999-psuh-tutorial.sh
</code></pre>
1399 <div class=
"paragraph"><p>You can get an idea of whether you created your new test script successfully
1400 by running
<code>make -C t test-lint
</code>, which will check for things like test number
1401 uniqueness, executable bit, and so on.
</p></div>
1404 <h3 id=
"local-test">Running Locally
</h3>
1405 <div class=
"paragraph"><p>Let
’s try and run locally:
</p></div>
1406 <div class=
"listingblock">
1407 <div class=
"content">
1409 $ cd t/
&& prove t9999-psuh-tutorial.sh
</code></pre>
1411 <div class=
"paragraph"><p>You can run the full test suite and ensure
<code>git-psuh
</code> didn
’t break anything:
</p></div>
1412 <div class=
"listingblock">
1413 <div class=
"content">
1415 $ prove -j$(nproc) --shuffle t[
0-
9]*.sh
</code></pre>
1417 <div class=
"admonitionblock">
1420 <div class=
"title">Note
</div>
1422 <td class=
"content">You can also do this with
<code>make test
</code> or use any testing harness which can
1423 speak TAP.
<code>prove
</code> can run concurrently.
<code>shuffle
</code> randomizes the order the
1424 tests are run in, which makes them resilient against unwanted inter-test
1425 dependencies.
<code>prove
</code> also makes the output nicer.
</td>
1428 <div class=
"paragraph"><p>Go ahead and commit this change, as well.
</p></div>
1433 <h2 id=
"ready-to-share">Getting Ready to Share: Anatomy of a Patch Series
</h2>
1434 <div class=
"sectionbody">
1435 <div class=
"paragraph"><p>You may have noticed already that the Git project performs its code reviews via
1436 emailed patches, which are then applied by the maintainer when they are ready
1437 and approved by the community. The Git project does not accept contributions from
1438 pull requests, and the patches emailed for review need to be formatted a
1439 specific way.
</p></div>
1440 <div class=
"paragraph"><p>Before taking a look at how to convert your commits into emailed patches,
1441 let
’s analyze what the end result, a
"patch series", looks like. Here is an
1442 <a href=
"https://lore.kernel.org/git/pull.1218.git.git.1645209647.gitgitgadget@gmail.com/">example
</a> of the summary view for a patch series on the web interface of
1443 the
<a href=
"https://lore.kernel.org/git/">Git mailing list archive
</a>:
</p></div>
1444 <div class=
"listingblock">
1445 <div class=
"content">
1446 <pre><code>2022-
02-
18 18:
40 [PATCH
0/
3] libify reflog John Cai via GitGitGadget
1447 2022-
02-
18 18:
40 ` [PATCH
1/
3] reflog: libify delete reflog function and helpers John Cai via GitGitGadget
1448 2022-
02-
18 19:
10 ` Ævar Arnfjörð Bjarmason [this message]
1449 2022-
02-
18 19:
39 ` Taylor Blau
1450 2022-
02-
18 19:
48 ` Ævar Arnfjörð Bjarmason
1451 2022-
02-
18 19:
35 ` Taylor Blau
1452 2022-
02-
21 1:
43 ` John Cai
1453 2022-
02-
21 1:
50 ` Taylor Blau
1454 2022-
02-
23 19:
50 ` John Cai
1455 2022-
02-
18 20:
00 ` // other replies elided
1456 2022-
02-
18 18:
40 ` [PATCH
2/
3] reflog: call reflog_delete from reflog.c John Cai via GitGitGadget
1457 2022-
02-
18 19:
15 ` Ævar Arnfjörð Bjarmason
1458 2022-
02-
18 20:
26 ` Junio C Hamano
1459 2022-
02-
18 18:
40 ` [PATCH
3/
3] stash: call reflog_delete from reflog.c John Cai via GitGitGadget
1460 2022-
02-
18 19:
20 ` Ævar Arnfjörð Bjarmason
1461 2022-
02-
19 0:
21 ` Taylor Blau
1462 2022-
02-
22 2:
36 ` John Cai
1463 2022-
02-
22 10:
51 ` Ævar Arnfjörð Bjarmason
1464 2022-
02-
18 19:
29 ` [PATCH
0/
3] libify reflog Ævar Arnfjörð Bjarmason
1465 2022-
02-
22 18:
30 ` [PATCH v2
0/
3] libify reflog John Cai via GitGitGadget
1466 2022-
02-
22 18:
30 ` [PATCH v2
1/
3] stash: add test to ensure reflog --rewrite --updatref behavior John Cai via GitGitGadget
1467 2022-
02-
23 8:
54 ` Ævar Arnfjörð Bjarmason
1468 2022-
02-
23 21:
27 ` Junio C Hamano
1469 // continued
</code></pre>
1471 <div class=
"paragraph"><p>We can note a few things:
</p></div>
1472 <div class=
"ulist"><ul>
1475 Each commit is sent as a separate email, with the commit message title as
1476 subject, prefixed with
"[PATCH <em>i</em>/<em>n</em>]" for the
<em>i
</em>-th commit of an
1477 <em>n
</em>-commit series.
1482 Each patch is sent as a reply to an introductory email called the
<em>cover
1483 letter
</em> of the series, prefixed
"[PATCH 0/<em>n</em>]".
1488 Subsequent iterations of the patch series are labelled
"PATCH v2",
"PATCH
1489 v3", etc. in place of
"PATCH". For example,
"[PATCH v2 1/3]" would be the first of
1490 three patches in the second iteration. Each iteration is sent with a new cover
1491 letter (like
"[PATCH v2 0/3]" above), itself a reply to the cover letter of the
1492 previous iteration (more on that below).
1496 <div class=
"admonitionblock">
1499 <div class=
"title">Note
</div>
1501 <td class=
"content">A single-patch topic is sent with
"[PATCH]",
"[PATCH v2]", etc. without
1502 <em>i
</em>/
<em>n
</em> numbering (in the above thread overview, no single-patch topic appears,
1507 <h3 id=
"cover-letter">The cover letter
</h3>
1508 <div class=
"paragraph"><p>In addition to an email per patch, the Git community also expects your patches
1509 to come with a cover letter. This is an important component of change
1510 submission as it explains to the community from a high level what you
’re trying
1511 to do, and why, in a way that
’s more apparent than just looking at your
1513 <div class=
"paragraph"><p>The title of your cover letter should be something which succinctly covers the
1514 purpose of your entire topic branch. It
’s often in the imperative mood, just
1515 like our commit message titles. Here is how we
’ll title our series:
</p></div>
1516 <div class=
"paragraph"><p>---
1517 Add the
<em>psuh
</em> command
1519 <div class=
"paragraph"><p>The body of the cover letter is used to give additional context to reviewers.
1520 Be sure to explain anything your patches don
’t make clear on their own, but
1521 remember that since the cover letter is not recorded in the commit history,
1522 anything that might be useful to future readers of the repository
’s history
1523 should also be in your commit messages.
</p></div>
1524 <div class=
"paragraph"><p>Here
’s an example body for
<code>psuh
</code>:
</p></div>
1525 <div class=
"listingblock">
1526 <div class=
"content">
1527 <pre><code>Our internal metrics indicate widespread interest in the command
1528 git-psuh - that is, many users are trying to use it, but finding it is
1529 unavailable, using some unknown workaround instead.
1531 The following handful of patches add the psuh command and implement some
1532 handy features on top of it.
1534 This patchset is part of the MyFirstContribution tutorial and should not
1535 be merged.
</code></pre>
1537 <div class=
"paragraph"><p>At this point the tutorial diverges, in order to demonstrate two
1538 different methods of formatting your patchset and getting it reviewed.
</p></div>
1539 <div class=
"paragraph"><p>The first method to be covered is GitGitGadget, which is useful for those
1540 already familiar with GitHub
’s common pull request workflow. This method
1541 requires a GitHub account.
</p></div>
1542 <div class=
"paragraph"><p>The second method to be covered is
<code>git send-email
</code>, which can give slightly
1543 more fine-grained control over the emails to be sent. This method requires some
1544 setup which can change depending on your system and will not be covered in this
1546 <div class=
"paragraph"><p>Regardless of which method you choose, your engagement with reviewers will be
1547 the same; the review process will be covered after the sections on GitGitGadget
1548 and
<code>git send-email
</code>.
</p></div>
1553 <h2 id=
"howto-ggg">Sending Patches via GitGitGadget
</h2>
1554 <div class=
"sectionbody">
1555 <div class=
"paragraph"><p>One option for sending patches is to follow a typical pull request workflow and
1556 send your patches out via GitGitGadget. GitGitGadget is a tool created by
1557 Johannes Schindelin to make life as a Git contributor easier for those used to
1558 the GitHub PR workflow. It allows contributors to open pull requests against its
1559 mirror of the Git project, and does some magic to turn the PR into a set of
1560 emails and send them out for you. It also runs the Git continuous integration
1561 suite for you. It
’s documented at
<a href=
"https://gitgitgadget.github.io/">https://gitgitgadget.github.io/
</a>.
</p></div>
1563 <h3 id=
"create-fork">Forking
<code>git/git
</code> on GitHub
</h3>
1564 <div class=
"paragraph"><p>Before you can send your patch off to be reviewed using GitGitGadget, you will
1565 need to fork the Git project and upload your changes. First thing - make sure
1566 you have a GitHub account.
</p></div>
1567 <div class=
"paragraph"><p>Head to the
<a href=
"https://github.com/git/git">GitHub mirror
</a> and look for the Fork
1568 button. Place your fork wherever you deem appropriate and create it.
</p></div>
1571 <h3 id=
"upload-to-fork">Uploading to Your Own Fork
</h3>
1572 <div class=
"paragraph"><p>To upload your branch to your own fork, you
’ll need to add the new fork as a
1573 remote. You can use
<code>git remote -v
</code> to show the remotes you have added already.
1574 From your new fork
’s page on GitHub, you can press
"Clone or download" to get
1575 the URL; then you need to run the following to add, replacing your own URL and
1576 remote name for the examples provided:
</p></div>
1577 <div class=
"listingblock">
1578 <div class=
"content">
1579 <pre><code>$ git remote add remotename git@github.com:remotename/git.git
</code></pre>
1581 <div class=
"paragraph"><p>or to use the HTTPS URL:
</p></div>
1582 <div class=
"listingblock">
1583 <div class=
"content">
1584 <pre><code>$ git remote add remotename https://github.com/remotename/git/.git
</code></pre>
1586 <div class=
"paragraph"><p>Run
<code>git remote -v
</code> again and you should see the new remote showing up.
1587 <code>git fetch remotename
</code> (with the real name of your remote replaced) in order to
1588 get ready to push.
</p></div>
1589 <div class=
"paragraph"><p>Next, double-check that you
’ve been doing all your development in a new branch
1590 by running
<code>git branch
</code>. If you didn
’t, now is a good time to move your new
1591 commits to their own branch.
</p></div>
1592 <div class=
"paragraph"><p>As mentioned briefly at the beginning of this document, we are basing our work
1593 on
<code>master
</code>, so go ahead and update as shown below, or using your preferred
1595 <div class=
"listingblock">
1596 <div class=
"content">
1597 <pre><code>$ git checkout master
1599 $ git rebase master psuh
</code></pre>
1601 <div class=
"paragraph"><p>Finally, you
’re ready to push your new topic branch! (Due to our branch and
1602 command name choices, be careful when you type the command below.)
</p></div>
1603 <div class=
"listingblock">
1604 <div class=
"content">
1605 <pre><code>$ git push remotename psuh
</code></pre>
1607 <div class=
"paragraph"><p>Now you should be able to go and check out your newly created branch on GitHub.
</p></div>
1610 <h3 id=
"send-pr-ggg">Sending a PR to GitGitGadget
</h3>
1611 <div class=
"paragraph"><p>In order to have your code tested and formatted for review, you need to start by
1612 opening a Pull Request against
<code>gitgitgadget/git
</code>. Head to
1613 <a href=
"https://github.com/gitgitgadget/git">https://github.com/gitgitgadget/git
</a> and open a PR either with the
"New pull
1614 request" button or the convenient
"Compare & pull request" button that may
1615 appear with the name of your newly pushed branch.
</p></div>
1616 <div class=
"paragraph"><p>Review the PR
’s title and description, as they
’re used by GitGitGadget
1617 respectively as the subject and body of the cover letter for your change. Refer
1618 to
<a href=
"#cover-letter">"The cover letter"</a> above for advice on how to title your
1619 submission and what content to include in the description.
</p></div>
1620 <div class=
"admonitionblock">
1623 <div class=
"title">Note
</div>
1625 <td class=
"content">For single-patch contributions, your commit message should already be
1626 meaningful and explain at a high level the purpose (what is happening and why)
1627 of your patch, so you usually do not need any additional context. In that case,
1628 remove the PR description that GitHub automatically generates from your commit
1629 message (your PR description should be empty). If you do need to supply even
1630 more context, you can do so in that space and it will be appended to the email
1631 that GitGitGadget will send, between the three-dash line and the diffstat
1632 (see
<a href=
"#single-patch">Bonus Chapter: One-Patch Changes
</a> for how this looks once
1636 <div class=
"paragraph"><p>When you
’re happy, submit your pull request.
</p></div>
1639 <h3 id=
"run-ci-ggg">Running CI and Getting Ready to Send
</h3>
1640 <div class=
"paragraph"><p>If it
’s your first time using GitGitGadget (which is likely, as you
’re using
1641 this tutorial) then someone will need to give you permission to use the tool.
1642 As mentioned in the GitGitGadget documentation, you just need someone who
1643 already uses it to comment on your PR with
<code>/allow
<username
></code>. GitGitGadget
1644 will automatically run your PRs through the CI even without the permission given
1645 but you will not be able to
<code>/submit
</code> your changes until someone allows you to
1646 use the tool.
</p></div>
1647 <div class=
"admonitionblock">
1650 <div class=
"title">Note
</div>
1652 <td class=
"content">You can typically find someone who can
<code>/allow
</code> you on GitGitGadget by
1653 either examining recent pull requests where someone has been granted
<code>/allow
</code>
1654 (
<a href=
"https://github.com/gitgitgadget/git/pulls?utf8=%E2%9C%93&q=is%3Apr+is%3Aopen+%22%2Fallow%22">Search:
1655 is:pr is:open
"/allow"</a>), in which case both the author and the person who
1656 granted the
<code>/allow
</code> can now
<code>/allow
</code> you, or by inquiring on the
1657 <a href=
"https://web.libera.chat/#git-devel">#git-devel
</a> IRC channel on Libera Chat
1658 linking your pull request and asking for someone to
<code>/allow
</code> you.
</td>
1661 <div class=
"paragraph"><p>If the CI fails, you can update your changes with
<code>git rebase -i
</code> and push your
1662 branch again:
</p></div>
1663 <div class=
"listingblock">
1664 <div class=
"content">
1665 <pre><code>$ git push -f remotename psuh
</code></pre>
1667 <div class=
"paragraph"><p>In fact, you should continue to make changes this way up until the point when
1668 your patch is accepted into
<code>next
</code>.
</p></div>
1671 <h3 id=
"send-mail-ggg">Sending Your Patches
</h3>
1672 <div class=
"paragraph"><p>Now that your CI is passing and someone has granted you permission to use
1673 GitGitGadget with the
<code>/allow
</code> command, sending out for review is as simple as
1674 commenting on your PR with
<code>/submit
</code>.
</p></div>
1677 <h3 id=
"responding-ggg">Updating With Comments
</h3>
1678 <div class=
"paragraph"><p>Skip ahead to
<a href=
"#reviewing">Responding to Reviews
</a> for information on how to
1679 reply to review comments you will receive on the mailing list.
</p></div>
1680 <div class=
"paragraph"><p>Once you have your branch again in the shape you want following all review
1681 comments, you can submit again:
</p></div>
1682 <div class=
"listingblock">
1683 <div class=
"content">
1684 <pre><code>$ git push -f remotename psuh
</code></pre>
1686 <div class=
"paragraph"><p>Next, go look at your pull request against GitGitGadget; you should see the CI
1687 has been kicked off again. Now while the CI is running is a good time for you
1688 to modify your description at the top of the pull request thread; it will be
1689 used again as the cover letter. You should use this space to describe what
1690 has changed since your previous version, so that your reviewers have some idea
1691 of what they
’re looking at. When the CI is done running, you can comment once
1692 more with
<code>/submit
</code> - GitGitGadget will automatically add a v2 mark to your
1698 <h2 id=
"howto-git-send-email">Sending Patches with
<code>git send-email
</code></h2>
1699 <div class=
"sectionbody">
1700 <div class=
"paragraph"><p>If you don
’t want to use GitGitGadget, you can also use Git itself to mail your
1701 patches. Some benefits of using Git this way include finer grained control of
1702 subject line (for example, being able to use the tag [RFC PATCH] in the subject)
1703 and being able to send a
“dry run
” mail to yourself to ensure it all looks
1704 good before going out to the list.
</p></div>
1706 <h3 id=
"setup-git-send-email">Prerequisite: Setting Up
<code>git send-email
</code></h3>
1707 <div class=
"paragraph"><p>Configuration for
<code>send-email
</code> can vary based on your operating system and email
1708 provider, and so will not be covered in this tutorial, beyond stating that in
1709 many distributions of Linux,
<code>git-send-email
</code> is not packaged alongside the
1710 typical
<code>git
</code> install. You may need to install this additional package; there
1711 are a number of resources online to help you do so. You will also need to
1712 determine the right way to configure it to use your SMTP server; again, as this
1713 configuration can change significantly based on your system and email setup, it
1714 is out of scope for the context of this tutorial.
</p></div>
1717 <h3 id=
"format-patch">Preparing Initial Patchset
</h3>
1718 <div class=
"paragraph"><p>Sending emails with Git is a two-part process; before you can prepare the emails
1719 themselves, you
’ll need to prepare the patches. Luckily, this is pretty simple:
</p></div>
1720 <div class=
"listingblock">
1721 <div class=
"content">
1722 <pre><code>$ git format-patch --cover-letter -o psuh/ --base=auto psuh@{u}..psuh
</code></pre>
1724 <div class=
"olist arabic"><ol class=
"arabic">
1727 The
<code>--cover-letter
</code> option tells
<code>format-patch
</code> to create a
1728 cover letter template for you. You will need to fill in the
1729 template before you
’re ready to send - but for now, the template
1730 will be next to your other patches.
1735 The
<code>-o psuh/
</code> option tells
<code>format-patch
</code> to place the patch
1736 files into a directory. This is useful because
<code>git send-email
</code>
1737 can take a directory and send out all the patches from there.
1742 The
<code>--base=auto
</code> option tells the command to record the
"base
1743 commit", on which the recipient is expected to apply the patch
1744 series. The
<code>auto
</code> value will cause
<code>format-patch
</code> to compute
1745 the base commit automatically, which is the merge base of tip
1746 commit of the remote-tracking branch and the specified revision
1752 The
<code>psuh@{u}..psuh
</code> option tells
<code>format-patch
</code> to generate
1753 patches for the commits you created on the
<code>psuh
</code> branch since it
1754 forked from its upstream (which is
<code>origin/master
</code> if you
1755 followed the example in the
"Set up your workspace" section). If
1756 you are already on the
<code>psuh
</code> branch, you can just say
<code>@{u}
</code>,
1757 which means
"commits on the current branch since it forked from
1758 its upstream", which is the same thing.
1762 <div class=
"paragraph"><p>The command will make one patch file per commit. After you
1763 run, you can go have a look at each of the patches with your favorite text
1764 editor and make sure everything looks alright; however, it
’s not recommended to
1765 make code fixups via the patch file. It
’s a better idea to make the change the
1766 normal way using
<code>git rebase -i
</code> or by adding a new commit than by modifying a
1768 <div class=
"admonitionblock">
1771 <div class=
"title">Note
</div>
1773 <td class=
"content">Optionally, you can also use the
<code>--rfc
</code> flag to prefix your patch subject
1774 with
“[RFC PATCH]
” instead of
“[PATCH]
”. RFC stands for
“request for
1775 comments
” and indicates that while your code isn
’t quite ready for submission,
1776 you
’d like to begin the code review process. This can also be used when your
1777 patch is a proposal, but you aren
’t sure whether the community wants to solve
1778 the problem with that approach or not - to conduct a sort of design review. You
1779 may also see on the list patches marked
“WIP
” - this means they are incomplete
1780 but want reviewers to look at what they have so far. You can add this flag with
1781 <code>--subject-prefix=WIP
</code>.
</td>
1784 <div class=
"paragraph"><p>Check and make sure that your patches and cover letter template exist in the
1785 directory you specified - you
’re nearly ready to send out your review!
</p></div>
1788 <h3 id=
"preparing-cover-letter">Preparing Email
</h3>
1789 <div class=
"paragraph"><p>Since you invoked
<code>format-patch
</code> with
<code>--cover-letter
</code>, you
’ve already got a
1790 cover letter template ready. Open it up in your favorite editor.
</p></div>
1791 <div class=
"paragraph"><p>You should see a number of headers present already. Check that your
<code>From:
</code>
1792 header is correct. Then modify your
<code>Subject:
</code> (see
<a href=
"#cover-letter">above
</a> for
1793 how to choose good title for your patch series):
</p></div>
1794 <div class=
"listingblock">
1795 <div class=
"content">
1796 <pre><code>Subject: [PATCH
0/
7] Add the 'psuh' command
</code></pre>
1798 <div class=
"paragraph"><p>Make sure you retain the
“[PATCH
0/X]
” part; that
’s what indicates to the Git
1799 community that this email is the beginning of a patch series, and many
1800 reviewers filter their email for this type of flag.
</p></div>
1801 <div class=
"paragraph"><p>You
’ll need to add some extra parameters when you invoke
<code>git send-email
</code> to add
1802 the cover letter.
</p></div>
1803 <div class=
"paragraph"><p>Next you
’ll have to fill out the body of your cover letter. Again, see
1804 <a href=
"#cover-letter">above
</a> for what content to include.
</p></div>
1805 <div class=
"paragraph"><p>The template created by
<code>git format-patch --cover-letter
</code> includes a diffstat.
1806 This gives reviewers a summary of what they
’re in for when reviewing your topic.
1807 The one generated for
<code>psuh
</code> from the sample implementation looks like this:
</p></div>
1808 <div class=
"listingblock">
1809 <div class=
"content">
1810 <pre><code> Documentation/git-psuh.txt |
40 +++++++++++++++++++++
1813 builtin/psuh.c |
73 ++++++++++++++++++++++++++++++++++++++
1815 t/t9999-psuh-tutorial.sh |
12 +++++++
1816 6 files changed,
128 insertions(+)
1817 create mode
100644 Documentation/git-psuh.txt
1818 create mode
100644 builtin/psuh.c
1819 create mode
100755 t/t9999-psuh-tutorial.sh
</code></pre>
1821 <div class=
"paragraph"><p>Finally, the letter will include the version of Git used to generate the
1822 patches. You can leave that string alone.
</p></div>
1825 <h3 id=
"sending-git-send-email">Sending Email
</h3>
1826 <div class=
"paragraph"><p>At this point you should have a directory
<code>psuh/
</code> which is filled with your
1827 patches and a cover letter. Time to mail it out! You can send it like this:
</p></div>
1828 <div class=
"listingblock">
1829 <div class=
"content">
1830 <pre><code>$ git send-email --to=target@example.com psuh/*.patch
</code></pre>
1832 <div class=
"admonitionblock">
1835 <div class=
"title">Note
</div>
1837 <td class=
"content">Check
<code>git help send-email
</code> for some other options which you may find
1838 valuable, such as changing the Reply-to address or adding more CC and BCC lines.
</td>
1841 <div class=
"admonitionblock">
1844 <div class=
"title">Note
</div>
1846 <td class=
"content">If you
’re not sure whom to CC, running
<code>contrib/contacts/git-contacts
</code> can
1847 list potential reviewers. In addition, you can do
<code>git send-email
1848 --cc-cmd='perl contrib/contacts/git-contacts' feature/*.patch
</code><span class=
"footnote" id=
"_footnote_contrib-scripts"><br />[Scripts under
<code>contrib/
</code> are not part of the core
<code>git
</code> binary and must be called directly. Clone the Git codebase and run
<code>perl contrib/contacts/git-contacts
</code>.]
<br /></span> to
1849 automatically pass this list of emails to
<code>send-email
</code>.
</td>
1852 <div class=
"admonitionblock">
1855 <div class=
"title">Note
</div>
1857 <td class=
"content">When you are sending a real patch, it will go to
<a href=
"mailto:git@vger.kernel.org">git@vger.kernel.org
</a> - but
1858 please don
’t send your patchset from the tutorial to the real mailing list! For
1859 now, you can send it to yourself, to make sure you understand how it will look.
</td>
1862 <div class=
"paragraph"><p>After you run the command above, you will be presented with an interactive
1863 prompt for each patch that
’s about to go out. This gives you one last chance to
1864 edit or quit sending something (but again, don
’t edit code this way). Once you
1865 press
<code>y
</code> or
<code>a
</code> at these prompts your emails will be sent! Congratulations!
</p></div>
1866 <div class=
"paragraph"><p>Awesome, now the community will drop everything and review your changes. (Just
1867 kidding - be patient!)
</p></div>
1870 <h3 id=
"v2-git-send-email">Sending v2
</h3>
1871 <div class=
"paragraph"><p>This section will focus on how to send a v2 of your patchset. To learn what
1872 should go into v2, skip ahead to
<a href=
"#reviewing">Responding to Reviews
</a> for
1873 information on how to handle comments from reviewers.
</p></div>
1874 <div class=
"paragraph"><p>We
’ll reuse our
<code>psuh
</code> topic branch for v2. Before we make any changes, we
’ll
1875 mark the tip of our v1 branch for easy reference:
</p></div>
1876 <div class=
"listingblock">
1877 <div class=
"content">
1878 <pre><code>$ git checkout psuh
1879 $ git branch psuh-v1
</code></pre>
1881 <div class=
"paragraph"><p>Refine your patch series by using
<code>git rebase -i
</code> to adjust commits based upon
1882 reviewer comments. Once the patch series is ready for submission, generate your
1883 patches again, but with some new flags:
</p></div>
1884 <div class=
"listingblock">
1885 <div class=
"content">
1886 <pre><code>$ git format-patch -v2 --cover-letter -o psuh/ --range-diff master..psuh-v1 master..
</code></pre>
1888 <div class=
"paragraph"><p>The
<code>--range-diff master..psuh-v1
</code> parameter tells
<code>format-patch
</code> to include a
1889 range-diff between
<code>psuh-v1
</code> and
<code>psuh
</code> in the cover letter (see
1890 <a href=
"git-range-diff.html">git-range-diff(
1)
</a>). This helps tell reviewers about the differences
1891 between your v1 and v2 patches.
</p></div>
1892 <div class=
"paragraph"><p>The
<code>-v2
</code> parameter tells
<code>format-patch
</code> to output your patches
1893 as version
"2". For instance, you may notice that your v2 patches are
1894 all named like
<code>v2-
000n-my-commit-subject.patch
</code>.
<code>-v2
</code> will also format
1895 your patches by prefixing them with
"[PATCH v2]" instead of
"[PATCH]",
1896 and your range-diff will be prefaced with
"Range-diff against v1".
</p></div>
1897 <div class=
"paragraph"><p>After you run this command,
<code>format-patch
</code> will output the patches to the
<code>psuh/
</code>
1898 directory, alongside the v1 patches. Using a single directory makes it easy to
1899 refer to the old v1 patches while proofreading the v2 patches, but you will need
1900 to be careful to send out only the v2 patches. We will use a pattern like
1901 <code>psuh/v2-*.patch
</code> (not
<code>psuh/*.patch
</code>, which would match v1 and v2 patches).
</p></div>
1902 <div class=
"paragraph"><p>Edit your cover letter again. Now is a good time to mention what
’s different
1903 between your last version and now, if it
’s something significant. You do not
1904 need the exact same body in your second cover letter; focus on explaining to
1905 reviewers the changes you
’ve made that may not be as visible.
</p></div>
1906 <div class=
"paragraph"><p>You will also need to go and find the Message-ID of your previous cover letter.
1907 You can either note it when you send the first series, from the output of
<code>git
1908 send-email
</code>, or you can look it up on the
1909 <a href=
"https://lore.kernel.org/git">mailing list
</a>. Find your cover letter in the
1910 archives, click on it, then click
"permalink" or
"raw" to reveal the Message-ID
1911 header. It should match:
</p></div>
1912 <div class=
"listingblock">
1913 <div class=
"content">
1914 <pre><code>Message-ID:
<foo
.12345.author@example.com
></code></pre>
1916 <div class=
"paragraph"><p>Your Message-ID is
<code><foo
.12345.author@example.com
></code>. This example will be used
1917 below as well; make sure to replace it with the correct Message-ID for your
1918 <strong>previous cover letter
</strong> - that is, if you
’re sending v2, use the Message-ID
1919 from v1; if you
’re sending v3, use the Message-ID from v2.
</p></div>
1920 <div class=
"paragraph"><p>While you
’re looking at the email, you should also note who is CC
’d, as it
’s
1921 common practice in the mailing list to keep all CCs on a thread. You can add
1922 these CC lines directly to your cover letter with a line like so in the header
1923 (before the Subject line):
</p></div>
1924 <div class=
"listingblock">
1925 <div class=
"content">
1926 <pre><code>CC: author@example.com, Othe R
<other@example.com
></code></pre>
1928 <div class=
"paragraph"><p>Now send the emails again, paying close attention to which messages you pass in
1929 to the command:
</p></div>
1930 <div class=
"listingblock">
1931 <div class=
"content">
1932 <pre><code>$ git send-email --to=target@example.com
1933 --in-reply-to=
"<foo.12345.author@example.com>"
1934 psuh/v2-*.patch
</code></pre>
1938 <h3 id=
"single-patch">Bonus Chapter: One-Patch Changes
</h3>
1939 <div class=
"paragraph"><p>In some cases, your very small change may consist of only one patch. When that
1940 happens, you only need to send one email. Your commit message should already be
1941 meaningful and explain at a high level the purpose (what is happening and why)
1942 of your patch, but if you need to supply even more context, you can do so below
1943 the
<code>---
</code> in your patch. Take the example below, which was generated with
<code>git
1944 format-patch
</code> on a single commit, and then edited to add the content between
1945 the
<code>---
</code> and the diffstat.
</p></div>
1946 <div class=
"listingblock">
1947 <div class=
"content">
1948 <pre><code>From
1345bbb3f7ac74abde040c12e737204689a72723 Mon Sep
17 00:
00:
00 2001
1949 From: A U Thor
<author@example.com
>
1950 Date: Thu,
18 Apr
2019 15:
11:
02 -
0700
1951 Subject: [PATCH] README: change the grammar
1953 I think it looks better this way. This part of the commit message will
1954 end up in the commit-log.
1956 Signed-off-by: A U Thor
<author@example.com
>
1958 Let's have a wild discussion about grammar on the mailing list. This
1959 part of my email will never end up in the commit log. Here is where I
1960 can add additional context to the mailing list about my intent, outside
1961 of the context of the commit log. This section was added after `git
1962 format-patch` was run, by editing the patch file in a text editor.
1965 1 file changed,
1 insertion(+),
1 deletion(-)
1967 diff --git a/README.md b/README.md
1968 index
88f126184c.
.38da593a60
100644
1972 Git - fast, scalable, distributed revision control system
1973 =========================================================
1975 -Git is a fast, scalable, distributed revision control system with an
1976 +Git is a fast, scalable, and distributed revision control system with an
1977 unusually rich command set that provides both high-level operations
1978 and full access to internals.
1981 2.21.0.392.gf8f6787159e-goog
</code></pre>
1987 <h2 id=
"now-what">My Patch Got Emailed - Now What?
</h2>
1988 <div class=
"sectionbody">
1989 <div class=
"paragraph"><p>Please give reviewers enough time to process your initial patch before
1990 sending an updated version. That is, resist the temptation to send a new
1991 version immediately, because others may have already started reviewing
1992 your initial version.
</p></div>
1993 <div class=
"paragraph"><p>While waiting for review comments, you may find mistakes in your initial
1994 patch, or perhaps realize a different and better way to achieve the goal
1995 of the patch. In this case you may communicate your findings to other
1996 reviewers as follows:
</p></div>
1997 <div class=
"ulist"><ul>
2000 If the mistakes you found are minor, send a reply to your patch as if
2001 you were a reviewer and mention that you will fix them in an
2007 On the other hand, if you think you want to change the course so
2008 drastically that reviews on the initial patch would be a waste of
2009 time (for everyone involved), retract the patch immediately with
2010 a reply like
"I am working on a much better approach, so please
2011 ignore this patch and wait for the updated version."
2015 <div class=
"paragraph"><p>Now, the above is a good practice if you sent your initial patch
2016 prematurely without polish. But a better approach of course is to avoid
2017 sending your patch prematurely in the first place.
</p></div>
2018 <div class=
"paragraph"><p>Please be considerate of the time needed by reviewers to examine each
2019 new version of your patch. Rather than seeing the initial version right
2020 now (followed by several
"oops, I like this version better than the
2021 previous one" patches over
2 days), reviewers would strongly prefer if a
2022 single polished version came
2 days later instead, and that version with
2023 fewer mistakes were the only one they would need to review.
</p></div>
2025 <h3 id=
"reviewing">Responding to Reviews
</h3>
2026 <div class=
"paragraph"><p>After a few days, you will hopefully receive a reply to your patchset with some
2027 comments. Woohoo! Now you can get back to work.
</p></div>
2028 <div class=
"paragraph"><p>It
’s good manners to reply to each comment, notifying the reviewer that you have
2029 made the change suggested, feel the original is better, or that the comment
2030 inspired you to do something a new way which is superior to both the original
2031 and the suggested change. This way reviewers don
’t need to inspect your v2 to
2032 figure out whether you implemented their comment or not.
</p></div>
2033 <div class=
"paragraph"><p>Reviewers may ask you about what you wrote in the patchset, either in
2034 the proposed commit log message or in the changes themselves. You
2035 should answer these questions in your response messages, but often the
2036 reason why reviewers asked these questions to understand what you meant
2037 to write is because your patchset needed clarification to be understood.
</p></div>
2038 <div class=
"paragraph"><p>Do not be satisfied by just answering their questions in your response
2039 and hear them say that they now understand what you wanted to say.
2040 Update your patches to clarify the points reviewers had trouble with,
2041 and prepare your v2; the words you used to explain your v1 to answer
2042 reviewers' questions may be useful thing to use. Your goal is to make
2043 your v2 clear enough so that it becomes unnecessary for you to give the
2044 same explanation to the next person who reads it.
</p></div>
2045 <div class=
"paragraph"><p>If you are going to push back on a comment, be polite and explain why you feel
2046 your original is better; be prepared that the reviewer may still disagree with
2047 you, and the rest of the community may weigh in on one side or the other. As
2048 with all code reviews, it
’s important to keep an open mind to doing something a
2049 different way than you originally planned; other reviewers have a different
2050 perspective on the project than you do, and may be thinking of a valid side
2051 effect which had not occurred to you. It is always okay to ask for clarification
2052 if you aren
’t sure why a change was suggested, or what the reviewer is asking
2053 you to do.
</p></div>
2054 <div class=
"paragraph"><p>Make sure your email client has a plaintext email mode and it is turned on; the
2055 Git list rejects HTML email. Please also follow the mailing list etiquette
2057 <a href=
"https://kernel.googlesource.com/pub/scm/git/git/+/todo/MaintNotes">Maintainer
’s
2058 Note
</a>, which are similar to etiquette rules in most open source communities
2059 surrounding bottom-posting and inline replies.
</p></div>
2060 <div class=
"paragraph"><p>When you
’re making changes to your code, it is cleanest - that is, the resulting
2061 commits are easiest to look at - if you use
<code>git rebase -i
</code> (interactive
2062 rebase). Take a look at this
2063 <a href=
"https://www.oreilly.com/library/view/git-pocket-guide/9781449327507/ch10.html">overview
</a>
2064 from O
’Reilly. The general idea is to modify each commit which requires changes;
2065 this way, instead of having a patch A with a mistake, a patch B which was fine
2066 and required no upstream reviews in v1, and a patch C which fixes patch A for
2067 v2, you can just ship a v2 with a correct patch A and correct patch B. This is
2068 changing history, but since it
’s local history which you haven
’t shared with
2069 anyone, that is okay for now! (Later, it may not make sense to do this; take a
2070 look at the section below this one for some context.)
</p></div>
2073 <h3 id=
"after-approval">After Review Approval
</h3>
2074 <div class=
"paragraph"><p>The Git project has four integration branches:
<code>seen
</code>,
<code>next
</code>,
<code>master
</code>, and
2075 <code>maint
</code>. Your change will be placed into
<code>seen
</code> fairly early on by the maintainer
2076 while it is still in the review process; from there, when it is ready for wider
2077 testing, it will be merged into
<code>next
</code>. Plenty of early testers use
<code>next
</code> and
2078 may report issues. Eventually, changes in
<code>next
</code> will make it to
<code>master
</code>,
2079 which is typically considered stable. Finally, when a new release is cut,
2080 <code>maint
</code> is used to base bugfixes onto. As mentioned at the beginning of this
2081 document, you can read
<code>Documents/SubmittingPatches
</code> for some more info about
2082 the use of the various integration branches.
</p></div>
2083 <div class=
"paragraph"><p>Back to now: your code has been lauded by the upstream reviewers. It is perfect.
2084 It is ready to be accepted. You don
’t need to do anything else; the maintainer
2085 will merge your topic branch to
<code>next
</code> and life is good.
</p></div>
2086 <div class=
"paragraph"><p>However, if you discover it isn
’t so perfect after this point, you may need to
2087 take some special steps depending on where you are in the process.
</p></div>
2088 <div class=
"paragraph"><p>If the maintainer has announced in the
"What’s cooking in git.git" email that
2089 your topic is marked for
<code>next
</code> - that is, that they plan to merge it to
<code>next
</code>
2090 but have not yet done so - you should send an email asking the maintainer to
2091 wait a little longer:
"I’ve sent v4 of my series and you marked it for <code>next</code>,
2092 but I need to change this and that - please wait for v5 before you merge it."</p></div>
2093 <div class=
"paragraph"><p>If the topic has already been merged to
<code>next
</code>, rather than modifying your
2094 patches with
<code>git rebase -i
</code>, you should make further changes incrementally -
2095 that is, with another commit, based on top of the maintainer
’s topic branch as
2096 detailed in
<a href=
"https://github.com/gitster/git">https://github.com/gitster/git
</a>. Your work is still in the same topic
2097 but is now incremental, rather than a wholesale rewrite of the topic branch.
</p></div>
2098 <div class=
"paragraph"><p>The topic branches in the maintainer
’s GitHub are mirrored in GitGitGadget, so
2099 if you
’re sending your reviews out that way, you should be sure to open your PR
2100 against the appropriate GitGitGadget/Git branch.
</p></div>
2101 <div class=
"paragraph"><p>If you
’re using
<code>git send-email
</code>, you can use it the same way as before, but you
2102 should generate your diffs from
<code><topic
>..
<mybranch
></code> and base your work on
2103 <code><topic
></code> instead of
<code>master
</code>.
</p></div>
2108 <div id=
"footnotes"><hr /></div>
2110 <div id=
"footer-text">
2112 2024-
05-
01 10:
56:
52 PDT