Fetch last change (revision) info in a separate action that can run

every build, instead of having it occur as a side effect of updating
some other target for which we want to use normal up-to-date checks.
BUG=none
TEST=none
Review URL: http://codereview.chromium.org/118192

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@17634 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 155 insertions, 0 deletions

diff --git a/build/util/build_util.gyp b/build/util/build_util.gyp
new file mode 100644
index 0000000..0624ab5
--- /dev/null
+++ b/build/util/build_util.gyp
@@ -0,0 +1,34 @@
+# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'includes': [
+    '../common.gypi',
+  ],
+  'targets': [
+    {
+      'target_name': 'lastchange',
+      'type': 'none',
+      'variables': {
+        'lastchange_out_path': '<(SHARED_INTERMEDIATE_DIR)/build/LASTCHANGE',
+      },
+      'actions': [
+        {
+          'action_name': 'lastchange',
+          'inputs': [
+            'lastchange.py',
+          ],
+          'outputs': [
+            '<(lastchange_out_path)',
+            '<(lastchange_out_path).always',
+          ],
+          'action': [
+            'python', '<@(_inputs)', '-o', '<(lastchange_out_path)',
+          ],
+          'message': 'Extracting last change to <(lastchange_out_path)'
+        },
+      ],
+    },
+  ]
+}
diff --git a/build/util/lastchange.py b/build/util/lastchange.py
new file mode 100644
index 0000000..3bac762
--- /dev/null
+++ b/build/util/lastchange.py
@@ -0,0 +1,121 @@
+#!/usr/bin/env python
+# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+lastchange.py -- Chromium revision fetching utility.
+"""
+
+import optparse
+import os
+import re
+import subprocess
+import sys
+
+
+def svn_fetch_revision():
+  """
+  Fetch the Subversion revision for the local tree.
+
+  Errors are swallowed.
+  """
+  try:
+    p = subprocess.Popen(['svn', 'info'],
+                         stdout=subprocess.PIPE,
+                         stderr=subprocess.PIPE)
+  except OSError:
+    # 'svn' is apparently either not installed or not executable.
+    return None
+  revision = None
+  if p:
+    svn_re = re.compile('^Revision:\s+(\S+)$', 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.
+  """
+  try:
+    p = subprocess.Popen(['git', 'log', '-1'],
+                         stdout=subprocess.PIPE,
+                         stderr=subprocess.PIPE)
+  except OSError:
+    # 'git' is apparently either not installed or not executable.
+    return None
+  id = None
+  if p:
+    git_re = re.compile('^\s*git-svn-id:\s+(\S+)@(\d+)', re.M)
+    m = git_re.search(p.stdout.read())
+    if m:
+      id = m.group(1)
+  return id
+
+
+def fetch_change():
+  """
+  Returns the last change, from some appropriate revision control system.
+  """
+  change = svn_fetch_revision()
+  if not change and sys.platform in ('linux2',):
+    change = git_fetch_id()
+  if not change:
+    change = '0'
+  return change
+
+
+def write_if_changed(file_name, contents):
+  """
+  Writes the specified contents to the specified file_name
+  iff the contents are different than the current contents.
+  """
+  try:
+    old_contents = open(file_name, 'r').read()
+  except EnvironmentError:
+    pass
+  else:
+    if contents == old_contents:
+      return
+    os.unlink(file_name)
+  open(file_name, 'w').write(contents)
+
+
+def main(argv=None):
+  if argv is None:
+    argv = sys.argv
+
+  parser = optparse.OptionParser(usage="lastchange.py [-h] [[-o] FILE]")
+  parser.add_option("-o", "--output", metavar="FILE",
+                    help="write last change to FILE")
+  opts, args = parser.parse_args(argv[1:])
+
+  out_file = opts.output
+
+  while len(args) and out_file is None:
+    if out_file is None:
+      out_file = args.pop(0)
+  if args:
+    sys.stderr.write('Unexpected arguments: %r\n\n' % args)
+    parser.print_help()
+    sys.exit(2)
+
+  change = fetch_change()
+
+  contents = "LASTCHANGE=%s\n" % change
+
+  if out_file:
+    write_if_changed(out_file, contents)
+  else:
+    sys.stdout.write(contents)
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())