git/merge-tree.c

   1 #include "cache.h"
   2 #include "tree-walk.h"
   3 #include "xdiff-interface.h"
   4 #include "blob.h"
   5
   6 static const char merge_tree_usage[] = "git-merge-tree <base-tree> <branch1> <branch2>";
   7 static int resolve_directories = 1;
   8
   9 struct merge_list {
  10         struct merge_list *next;
  11         struct merge_list *link;        /* other stages for this object */
  12
  13         unsigned int stage : 2,
  14                      flags : 30;
  15         unsigned int mode;
  16         const char *path;
  17         struct blob *blob;
  18 };
  19
  20 static struct merge_list *merge_result, **merge_result_end = &merge_result;
  21
  22 static void add_merge_entry(struct merge_list *entry)
  23 {
  24         *merge_result_end = entry;
  25         merge_result_end = &entry->next;
  26 }
  27
  28 static void merge_trees(struct tree_desc t[3], const char *base);
  29
  30 static const char *explanation(struct merge_list *entry)
  31 {
  32         switch (entry->stage) {
  33         case 0:
  34                 return "merged";
  35         case 3:
  36                 return "added in remote";
  37         case 2:
  38                 if (entry->link)
  39                         return "added in both";
  40                 return "added in local";
  41         }
  42
  43         /* Existed in base */
  44         entry = entry->link;
  45         if (!entry)
  46                 return "removed in both";
  47
  48         if (entry->link)
  49                 return "changed in both";
  50
  51         if (entry->stage == 3)
  52                 return "removed in local";
  53         return "removed in remote";
  54 }
  55
  56 extern void *merge_file(struct blob *, struct blob *, struct blob *, unsigned long *);
  57
  58 static void *result(struct merge_list *entry, unsigned long *size)
  59 {
  60         enum object_type type;
  61         struct blob *base, *our, *their;
  62
  63         if (!entry->stage)
  64                 return read_sha1_file(entry->blob->object.sha1, &type, size);
  65         base = NULL;
  66         if (entry->stage == 1) {
  67                 base = entry->blob;
  68                 entry = entry->link;
  69         }
  70         our = NULL;
  71         if (entry && entry->stage == 2) {
  72                 our = entry->blob;
  73                 entry = entry->link;
  74         }
  75         their = NULL;
  76         if (entry)
  77                 their = entry->blob;
  78         return merge_file(base, our, their, size);
  79 }
  80
  81 static void *origin(struct merge_list *entry, unsigned long *size)
  82 {
  83         enum object_type type;
  84         while (entry) {
  85                 if (entry->stage == 2)
  86                         return read_sha1_file(entry->blob->object.sha1, &type, size);
  87                 entry = entry->link;
  88         }
  89         return NULL;
  90 }
  91
  92 static int show_outf(void *priv_, mmbuffer_t *mb, int nbuf)
  93 {
  94         int i;
  95         for (i = 0; i < nbuf; i++)
  96                 printf("%.*s", (int) mb[i].size, mb[i].ptr);
  97         return 0;
  98 }
  99
 100 static void show_diff(struct merge_list *entry)
 101 {
 102         unsigned long size;
 103         mmfile_t src, dst;
 104         xpparam_t xpp;
 105         xdemitconf_t xecfg;
 106         xdemitcb_t ecb;
 107
 108         xpp.flags = XDF_NEED_MINIMAL;
 109         memset(&xecfg, 0, sizeof(xecfg));
 110         xecfg.ctxlen = 3;
 111         ecb.outf = show_outf;
 112         ecb.priv = NULL;
 113
 114         src.ptr = origin(entry, &size);
 115         if (!src.ptr)
 116                 size = 0;
 117         src.size = size;
 118         dst.ptr = result(entry, &size);
 119         if (!dst.ptr)
 120                 size = 0;
 121         dst.size = size;
 122         xdl_diff(&src, &dst, &xpp, &xecfg, &ecb);
 123         free(src.ptr);
 124         free(dst.ptr);
 125 }
 126
 127 static void show_result_list(struct merge_list *entry)
 128 {
 129         printf("%s\n", explanation(entry));
 130         do {
 131                 struct merge_list *link = entry->link;
 132                 static const char *desc[4] = { "result", "base", "our", "their" };
 133                 printf("  %-6s %o %s %s\n", desc[entry->stage], entry->mode, sha1_to_hex(entry->blob->object.sha1), entry->path);
 134                 entry = link;
 135         } while (entry);
 136 }
 137
 138 static void show_result(void)
 139 {
 140         struct merge_list *walk;
 141
 142         walk = merge_result;
 143         while (walk) {
 144                 show_result_list(walk);
 145                 show_diff(walk);
 146                 walk = walk->next;
 147         }
 148 }
 149
 150 /* An empty entry never compares same, not even to another empty entry */
 151 static int same_entry(struct name_entry *a, struct name_entry *b)
 152 {
 153         return  a->sha1 &&
 154                 b->sha1 &&
 155                 !hashcmp(a->sha1, b->sha1) &&
 156                 a->mode == b->mode;
 157 }
 158
 159 static struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
 160 {
 161         struct merge_list *res = xmalloc(sizeof(*res));
 162
 163         memset(res, 0, sizeof(*res));
 164         res->stage = stage;
 165         res->path = path;
 166         res->mode = mode;
 167         res->blob = lookup_blob(sha1);
 168         return res;
 169 }
 170
 171 static void resolve(const char *base, struct name_entry *branch1, struct name_entry *result)
 172 {
 173         struct merge_list *orig, *final;
 174         const char *path;
 175
 176         /* If it's already branch1, don't bother showing it */
 177         if (!branch1)
 178                 return;
 179
 180         path = xstrdup(mkpath("%s%s", base, result->path));
 181         orig = create_entry(2, branch1->mode, branch1->sha1, path);
 182         final = create_entry(0, result->mode, result->sha1, path);
 183
 184         final->link = orig;
 185
 186         add_merge_entry(final);
 187 }
 188
 189 static int unresolved_directory(const char *base, struct name_entry n[3])
 190 {
 191         int baselen, pathlen;
 192         char *newbase;
 193         struct name_entry *p;
 194         struct tree_desc t[3];
 195         void *buf0, *buf1, *buf2;
 196
 197         if (!resolve_directories)
 198                 return 0;
 199         p = n;
 200         if (!p->mode) {
 201                 p++;
 202                 if (!p->mode)
 203                         p++;
 204         }
 205         if (!S_ISDIR(p->mode))
 206                 return 0;
 207         baselen = strlen(base);
 208         pathlen = tree_entry_len(p->path, p->sha1);
 209         newbase = xmalloc(baselen + pathlen + 2);
 210         memcpy(newbase, base, baselen);
 211         memcpy(newbase + baselen, p->path, pathlen);
 212         memcpy(newbase + baselen + pathlen, "/", 2);
 213
 214         buf0 = fill_tree_descriptor(t+0, n[0].sha1);
 215         buf1 = fill_tree_descriptor(t+1, n[1].sha1);
 216         buf2 = fill_tree_descriptor(t+2, n[2].sha1);
 217         merge_trees(t, newbase);
 218
 219         free(buf0);
 220         free(buf1);
 221         free(buf2);
 222         free(newbase);
 223         return 1;
 224 }
 225
 226
 227 static struct merge_list *link_entry(unsigned stage, const char *base, struct name_entry *n, struct merge_list *entry)
 228 {
 229         const char *path;
 230         struct merge_list *link;
 231
 232         if (!n->mode)
 233                 return entry;
 234         if (entry)
 235                 path = entry->path;
 236         else
 237                 path = xstrdup(mkpath("%s%s", base, n->path));
 238         link = create_entry(stage, n->mode, n->sha1, path);
 239         link->link = entry;
 240         return link;
 241 }
 242
 243 static void unresolved(const char *base, struct name_entry n[3])
 244 {
 245         struct merge_list *entry = NULL;
 246
 247         if (unresolved_directory(base, n))
 248                 return;
 249
 250         /*
 251          * Do them in reverse order so that the resulting link
 252          * list has the stages in order - link_entry adds new
 253          * links at the front.
 254          */
 255         entry = link_entry(3, base, n + 2, entry);
 256         entry = link_entry(2, base, n + 1, entry);
 257         entry = link_entry(1, base, n + 0, entry);
 258
 259         add_merge_entry(entry);
 260 }
 261
 262 /*
 263  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 264  * as the origin.
 265  *
 266  * This walks the (sorted) trees in lock-step, checking every possible
 267  * name. Note that directories automatically sort differently from other
 268  * files (see "base_name_compare"), so you'll never see file/directory
 269  * conflicts, because they won't ever compare the same.
 270  *
 271  * IOW, if a directory changes to a filename, it will automatically be
 272  * seen as the directory going away, and the filename being created.
 273  *
 274  * Think of this as a three-way diff.
 275  *
 276  * The output will be either:
 277  *  - successful merge
 278  *       "0 mode sha1 filename"
 279  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 280  *    in parallel with this too!
 281  *
 282  *  - conflict:
 283  *      "1 mode sha1 filename"
 284  *      "2 mode sha1 filename"
 285  *      "3 mode sha1 filename"
 286  *    where not all of the 1/2/3 lines may exist, of course.
 287  *
 288  * The successful merge rules are the same as for the three-way merge
 289  * in git-read-tree.
 290  */
 291 static void threeway_callback(int n, unsigned long mask, struct name_entry *entry, const char *base)
 292 {
 293         /* Same in both? */
 294         if (same_entry(entry+1, entry+2)) {
 295                 if (entry[0].sha1) {
 296                         resolve(base, NULL, entry+1);
 297                         return;
 298                 }
 299         }
 300
 301         if (same_entry(entry+0, entry+1)) {
 302                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 303                         resolve(base, entry+1, entry+2);
 304                         return;
 305                 }
 306         }
 307
 308         if (same_entry(entry+0, entry+2)) {
 309                 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 310                         resolve(base, NULL, entry+1);
 311                         return;
 312                 }
 313         }
 314
 315         unresolved(base, entry);
 316 }
 317
 318 static void merge_trees(struct tree_desc t[3], const char *base)
 319 {
 320         traverse_trees(3, t, base, threeway_callback);
 321 }
 322
 323 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 324 {
 325         unsigned char sha1[20];
 326         void *buf;
 327
 328         if (get_sha1(rev, sha1))
 329                 die("unknown rev %s", rev);
 330         buf = fill_tree_descriptor(desc, sha1);
 331         if (!buf)
 332                 die("%s is not a tree", rev);
 333         return buf;
 334 }
 335
 336 int main(int argc, char **argv)
 337 {
 338         struct tree_desc t[3];
 339         void *buf1, *buf2, *buf3;
 340
 341         if (argc != 4)
 342                 usage(merge_tree_usage);
 343
 344         setup_git_directory();
 345
 346         buf1 = get_tree_descriptor(t+0, argv[1]);
 347         buf2 = get_tree_descriptor(t+1, argv[2]);
 348         buf3 = get_tree_descriptor(t+2, argv[3]);
 349         merge_trees(t, "");
 350         free(buf1);
 351         free(buf2);
 352         free(buf3);
 353
 354         show_result();
 355         return 0;
 356 }