Automatically install Gerrit Code Review's commit-msg hook

Most users of repo are also using Gerrit Code Review, and will want
the commit-msg hook to be automatically installed into their local
projects so that Change-Ids are assigned when commits are created,
not when they are first uploaded.

(cherry picked from commit a949fa5d20
 but squashed with latest hook script from version 2.1.2)

Change-Id: Ie68b2d60ac85d8c2285d2e1e6a4536eb76695547
Signed-off-by: Shawn O. Pearce <sop@google.com>

hooks/commit-msg

@@ -0,0 +1,101 @@
+#!/bin/sh
+# From Gerrit Code Review 2.1.2-rc2-33-g7e30c72
+#
+# Part of Gerrit Code Review (http://code.google.com/p/gerrit/)
+#
+# Copyright (C) 2009 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+CHANGE_ID_AFTER="Bug|Issue"
+MSG="$1"
+
+# Check for, and add if missing, a unique Change-Id
+#
+add_ChangeId() {
+	clean_message=$(sed -e '
+		/^diff --git a\/.*/{
+			s///
+			q
+		}
+		/^Signed-off-by:/d
+		/^#/d
+	' "$MSG" | git stripspace)
+	if test -z "$clean_message"
+	then
+		return
+	fi
+
+	if grep -i '^Change-Id:' "$MSG" >/dev/null
+	then
+		return
+	fi
+
+	id=$(_gen_ChangeId)
+	perl -e '
+		$MSG = shift;
+		$id = shift;
+		$CHANGE_ID_AFTER = shift;
+
+		undef $/;
+		open(I, $MSG); $_ = <I>; close I;
+		s|^diff --git a/.*||ms;
+		s|^#.*$||mg;
+		exit unless $_;
+
+		@message = split /\n/;
+		$haveFooter = 0;
+		$startFooter = @message;
+		for($line = @message - 1; $line >= 0; $line--) {
+			$_ = $message[$line];
+
+			($haveFooter++, next) if /^[a-zA-Z0-9-]+:/;
+			next if /^[ []/;
+			$startFooter = $line if ($haveFooter && /^\r?$/);
+			last;
+		}
+
+		@footer = @message[$startFooter+1..@message];
+		@message = @message[0..$startFooter];
+		push(@footer, "") unless @footer;
+
+		for ($line = 0; $line < @footer; $line++) {
+			$_ = $footer[$line];
+			next if /^($CHANGE_ID_AFTER):/i;
+			last;
+		}
+		splice(@footer, $line, 0, "Change-Id: I$id");
+
+		$_ = join("\n", @message, @footer);
+		open(O, ">$MSG"); print O; close O;
+	' "$MSG" "$id" "$CHANGE_ID_AFTER"
+}
+_gen_ChangeIdInput() {
+	echo "tree $(git write-tree)"
+	if parent=$(git rev-parse HEAD^0 2>/dev/null)
+	then
+		echo "parent $parent"
+	fi
+	echo "author $(git var GIT_AUTHOR_IDENT)"
+	echo "committer $(git var GIT_COMMITTER_IDENT)"
+	echo
+	printf '%s' "$clean_message"
+}
+_gen_ChangeId() {
+	_gen_ChangeIdInput |
+	git hash-object -t commit --stdin
+}
+
+
+add_ChangeId

project.py

@@ -1055,13 +1055,27 @@ class Project(object):
     if not os.path.exists(hooks):
       os.makedirs(hooks)
     for stock_hook in repo_hooks():
-      dst = os.path.join(hooks, os.path.basename(stock_hook))
+      name = os.path.basename(stock_hook)
+
+      if name in ('commit-msg') and not self.remote.review:
+        # Don't install a Gerrit Code Review hook if this
+        # project does not appear to use it for reviews.
+        #
+        continue
+
+      dst = os.path.join(hooks, name)
+      if os.path.islink(dst):
+        continue
+      if os.path.exists(dst):
+        if filecmp.cmp(stock_hook, dst, shallow=False):
+          os.remove(dst)
+        else:
+          _error("%s: Not replacing %s hook", self.relpath, name)
+          continue
       try:
         os.symlink(relpath(stock_hook, dst), dst)
       except OSError, e:
-        if e.errno == errno.EEXIST:
+        if e.errno == errno.EPERM:
-          pass
-        elif e.errno == errno.EPERM:
           raise GitError('filesystem must support symlinks')
         else:
           raise