lastchange.py: fix style, unify git codepath

1) Change style to match style guide.
2) Use "git svn info" so we can use the same parsing code for
   both git and svn.

TEST=ran manually

Review URL: http://codereview.chromium.org/6263009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72074 0039d316-1c4b-4281-b951-d872f2087c98

build/util/lastchange.py

@@ -14,61 +14,35 @@ import subprocess
 import sys
 
 
-def svn_fetch_revision():
+def FetchSVNRevision(command):
   """
   Fetch the Subversion revision for the local tree.
 
   Errors are swallowed.
   """
   try:
-    p = subprocess.Popen(['svn', 'info'],
-                         stdout=subprocess.PIPE,
-                         stderr=subprocess.PIPE,
-                         shell=(sys.platform=='win32'))
-  except OSError, e:
-    # 'svn' is apparently either not installed or not executable.
-    return None
-  revision = None
-  if p:
-    svn_re = re.compile('^Revision:\s+(\d+)', re.M)
-    m = svn_re.search(p.stdout.read())
-    if m:
-      revision = m.group(1)
-  return revision
-
-
-def git_fetch_id():
-  """
-  Fetch the GIT identifier for the local tree.
-
-  Errors are swallowed.
-  """
-  git_re = re.compile('^\s*git-svn-id:\s+(\S+)@(\d+)', re.M)
-  try:
-    proc = subprocess.Popen(['git', 'log', '-999'],
+    proc = subprocess.Popen(command,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE,
                             shell=(sys.platform=='win32'))
-    for line in proc.stdout:
-      match = git_re.search(line)
-      if match:
-        id = match.group(2)
-        if id:
-          proc.stdout.close()  # Cut pipe.
-          return id
   except OSError:
-    # 'git' is apparently either not installed or not executable.
-    pass
+    # command is apparently either not installed or not executable.
+    return None
+  if proc:
+    svn_re = re.compile('^Revision:\s+(\d+)', re.M)
+    match = svn_re.search(proc.stdout.read())
+    if match:
+      return match.group(1)
   return None
 
 
-def fetch_change(default_lastchange):
+def FetchChange(default_lastchange):
   """
   Returns the last change, from some appropriate revision control system.
   """
-  change = svn_fetch_revision()
+  change = FetchSVNRevision(['svn', 'info'])
   if not change and sys.platform in ('linux2',):
-    change = git_fetch_id()
+    change = FetchSVNRevision(['git', 'svn', 'info'])
   if not change:
     if default_lastchange and os.path.exists(default_lastchange):
       change = open(default_lastchange, 'r').read().strip()
@@ -77,7 +51,7 @@ def fetch_change(default_lastchange):
   return change
 
 
-def write_if_changed(file_name, contents):
+def WriteIfChanged(file_name, contents):
   """
   Writes the specified contents to the specified file_name
   iff the contents are different than the current contents.
@@ -114,12 +88,12 @@ def main(argv=None):
     parser.print_help()
     sys.exit(2)
 
-  change = fetch_change(opts.default_lastchange)
+  change = FetchChange(opts.default_lastchange)
 
   contents = "LASTCHANGE=%s\n" % change
 
   if out_file:
-    write_if_changed(out_file, contents)
+    WriteIfChanged(out_file, contents)
   else:
     sys.stdout.write(contents)