tools/gn/last_commit_position.py

   1 # Copyright 2014 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 """Writes the most recent "Cr-Commit-Position" value on the master branch
   6 to a C header file.
   7
   8 Usage: last_commit_position.py <dir> <outfile> <headerguard>
   9
  10   <dir>
  11     Some directory inside the repo to check. This will be used as the current
  12     directory when running git. It's best to pass the repo toplevel directory.
  13
  14   <outfile>
  15     C header file to write.
  16
  17   <headerguard>
  18     String to use as the header guard for the written file.
  19 """
  20
  21 import os
  22 import re
  23 import subprocess
  24 import sys
  25
  26 def RunGitCommand(directory, command):
  27   """
  28   Launches git subcommand.
  29
  30   Errors are swallowed.
  31
  32   Returns:
  33     A process object or None.
  34   """
  35   command = ['git'] + command
  36   # Force shell usage under cygwin. This is a workaround for
  37   # mysterious loss of cwd while invoking cygwin's git.
  38   # We can't just pass shell=True to Popen, as under win32 this will
  39   # cause CMD to be used, while we explicitly want a cygwin shell.
  40   if sys.platform == 'cygwin':
  41     command = ['sh', '-c', ' '.join(command)]
  42   try:
  43     proc = subprocess.Popen(command,
  44                             stdout=subprocess.PIPE,
  45                             stderr=subprocess.PIPE,
  46                             cwd=directory,
  47                             shell=(sys.platform=='win32'))
  48     return proc
  49   except OSError:
  50     return None
  51
  52
  53 def FetchCommitPosition(directory):
  54   regex = re.compile(r'\s*Cr-Commit-Position: refs/heads/master@\{#(\d+)\}\s*')
  55
  56   # Search this far backward in the git log. The commit position should be
  57   # close to the top. We allow some slop for long commit messages, and maybe
  58   # there were some local commits after the last "official" one. Having this
  59   # max prevents us from searching all history in the case of an error.
  60   max_lines = 2048
  61
  62   proc = RunGitCommand(directory, ['log'])
  63   for i in range(max_lines):
  64     line = proc.stdout.readline()
  65     if not line:
  66       return None
  67
  68     match = regex.match(line)
  69     if match:
  70       return match.group(1)
  71
  72   return None
  73
  74
  75 def WriteHeader(header_file, header_guard, value):
  76   with open(header_file, 'w') as f:
  77     f.write('''/* Generated by last_commit_position.py. */
  78
  79 #ifndef %(guard)s
  80 #define %(guard)s
  81
  82 #define LAST_COMMIT_POSITION "%(value)s"
  83
  84 #endif
  85 ''' % {'guard': header_guard, 'value': value})
  86
  87
  88 if len(sys.argv) != 4:
  89   print "Wrong number of arguments"
  90   sys.exit(1)
  91
  92 git_directory = sys.argv[1]
  93 output_file = sys.argv[2]
  94 header_guard = sys.argv[3]
  95
  96 value = FetchCommitPosition(git_directory)
  97 if not value:
  98   print "Could not get last commit position."
  99   sys.exit(1)
 100
 101 WriteHeader(output_file, header_guard, value)