Add an example hook script for checking valid commits

This script can give negative scores to commits with improperly formatted
commit messages.  This will help save reviewer's time and get developers in
the habbit of writing proper commit messages.

contrib/check-valid-commit.py

@@ -0,0 +1,104 @@
+#!/usr/bin/env python
+import commands
+import getopt
+import sys
+
+
+SSH_USER = 'bot'
+SSH_HOST = 'localhost'
+SSH_PORT = 29418
+SSH_COMMAND = 'ssh %s@%s -p %d gerrit approve ' % (SSH_USER, SSH_HOST, SSH_PORT)
+FAILURE_SCORE = '--code-review=-2'
+FAILURE_MESSAGE = 'This commit message does not match the standard.' \
+        + '  Please correct the commit message and upload a replacement patch.'
+PASS_SCORE = '--code-review=0'
+PASS_MESSAGE = ''
+
+def main():
+    change = None
+    project = None
+    branch = None
+    commit = None
+    patchset = None
+
+    try:
+        opts, args = getopt.getopt(sys.argv[1:], '', \
+            ['change=', 'project=', 'branch=', 'commit=', 'patchset='])
+    except getopt.GetoptError, err:
+        print 'Error: %s' % (err)
+        usage()
+        sys.exit(-1)
+
+    for arg, value in opts:
+        if arg == '--change':
+            change = value
+        elif arg == '--project':
+            project = value
+        elif arg == '--branch':
+            branch = value
+        elif arg == '--commit':
+            commit = value
+        elif arg == '--patchset':
+            patchset = value
+        else:
+            print 'Error: option %s not recognized' % (arg)
+            usage()
+            sys.exit(-1)
+
+    if change == None or project == None or branch == None \
+        or commit == None or patchset == None:
+        usage()
+        sys.exit(-1)
+
+    command = 'git cat-file commit %s' % (commit)
+    status, output = commands.getstatusoutput(command)
+
+    if status != 0:
+        print 'Error running \'%s\'. status: %s, output:\n\n%s' % \
+            (command, status, output)
+        sys.exit(-1)
+
+    commitMessage = output[(output.find('\n\n')+2):]
+    commitLines = commitMessage.split('\n')
+
+    if len(commitLines) > 1 and len(commitLines[1]) != 0:
+        fail(commit, 'Invalid commit summary.  The summary must be ' \
+            + 'one line followed by a blank line.')
+
+    i = 0
+    for line in commitLines:
+        i = i + 1
+        if len(line) > 80:
+            fail(commit, 'Line %d is over 80 characters.' % i)
+
+    passes(commit)
+
+def usage():
+    print 'Usage:\n'
+    print sys.argv[0] + ' --change <change id> --project <project name> ' \
+        + '--branch <branch> --commit <sha1> --patchset <patchset id>'
+
+def fail( commit, message ):
+    command = SSH_COMMAND + FAILURE_SCORE + ' -m \\\"' \
+        + _shell_escape( FAILURE_MESSAGE + '\n\n' + message) \
+        + '\\\" ' + commit
+    commands.getstatusoutput(command)
+    sys.exit(1)
+
+def passes( commit ):
+    command = SSH_COMMAND + PASS_SCORE + ' -m \\\"' \
+        + _shell_escape(PASS_MESSAGE) + ' \\\" ' + commit
+    commands.getstatusoutput(command)
+
+def _shell_escape(x):
+    s = ''
+    for c in x:
+        if c in '\n':
+            s = s + '\\\"$\'\\n\'\\\"'
+        else:
+            s = s + c
+    return s
+
+if __name__ == '__main__':
+    main()
+