diff --git a/hooks/commit-msg b/hooks/commit-msg
index 712921c9..172a1781 100755
--- a/hooks/commit-msg
+++ b/hooks/commit-msg
@@ -1,5 +1,5 @@
 #!/bin/sh
-# From Gerrit Code Review 2.1.2-rc2-33-g7e30c72
+# From Gerrit Code Review 2.5-rc0
 #
 # Part of Gerrit Code Review (http://code.google.com/p/gerrit/)
 #
@@ -24,71 +24,144 @@ MSG="$1"
 # Check for, and add if missing, a unique Change-Id
 #
 add_ChangeId() {
-	clean_message=$(sed -e '
+	clean_message=`sed -e '
 		/^diff --git a\/.*/{
 			s///
 			q
 		}
 		/^Signed-off-by:/d
 		/^#/d
-	' "$MSG" | git stripspace)
+	' "$MSG" | git stripspace`
 	if test -z "$clean_message"
 	then
 		return
 	fi
 
+	# Does Change-Id: already exist? if so, exit (no change).
 	if grep -i '^Change-Id:' "$MSG" >/dev/null
 	then
 		return
 	fi
 
-	id=$(_gen_ChangeId)
-	perl -e '
-		$MSG = shift;
-		$id = shift;
-		$CHANGE_ID_AFTER = shift;
+	id=`_gen_ChangeId`
+	T="$MSG.tmp.$$"
+	AWK=awk
+	if [ -x /usr/xpg4/bin/awk ]; then
+		# Solaris AWK is just too broken
+		AWK=/usr/xpg4/bin/awk
+	fi
 
-		undef $/;
-		open(I, $MSG); $_ = <I>; close I;
-		s|^diff --git a/.*||ms;
-		s|^#.*$||mg;
-		exit unless $_;
+	# How this works:
+	# - parse the commit message as (textLine+ blankLine*)*
+	# - assume textLine+ to be a footer until proven otherwise
+	# - exception: the first block is not footer (as it is the title)
+	# - read textLine+ into a variable
+	# - then count blankLines
+	# - once the next textLine appears, print textLine+ blankLine* as these
+	#   aren't footer
+	# - in END, the last textLine+ block is available for footer parsing
+	$AWK '
+	BEGIN {
+		# while we start with the assumption that textLine+
+		# is a footer, the first block is not.
+		isFooter = 0
+		footerComment = 0
+		blankLines = 0
+	}
 
-		@message = split /\n/;
-		$haveFooter = 0;
-		$startFooter = @message;
-		for($line = @message - 1; $line >= 0; $line--) {
-			$_ = $message[$line];
+	# Skip lines starting with "#" without any spaces before it.
+	/^#/ { next }
 
-			($haveFooter++, next) if /^[a-zA-Z0-9-]+:/;
-			next if /^[ []/;
-			$startFooter = $line if ($haveFooter && /^\r?$/);
-			last;
+	# Skip the line starting with the diff command and everything after it,
+	# up to the end of the file, assuming it is only patch data.
+	# If more than one line before the diff was empty, strip all but one.
+	/^diff --git a/ {
+		blankLines = 0
+		while (getline) { }
+		next
+	}
+
+	# Count blank lines outside footer comments
+	/^$/ && (footerComment == 0) {
+		blankLines++
+		next
+	}
+
+	# Catch footer comment
+	/^\[[a-zA-Z0-9-]+:/ && (isFooter == 1) {
+		footerComment = 1
+	}
+
+	/]$/ && (footerComment == 1) {
+		footerComment = 2
+	}
+
+	# We have a non-blank line after blank lines. Handle this.
+	(blankLines > 0) {
+		print lines
+		for (i = 0; i < blankLines; i++) {
+			print ""
 		}
 
-		@footer = @message[$startFooter+1..@message];
-		@message = @message[0..$startFooter];
-		push(@footer, "") unless @footer;
+		lines = ""
+		blankLines = 0
+		isFooter = 1
+		footerComment = 0
+	}
 
-		for ($line = 0; $line < @footer; $line++) {
-			$_ = $footer[$line];
-			next if /^($CHANGE_ID_AFTER):/i;
-			last;
+	# Detect that the current block is not the footer
+	(footerComment == 0) && (!/^\[?[a-zA-Z0-9-]+:/ || /^[a-zA-Z0-9-]+:\/\//) {
+		isFooter = 0
+	}
+
+	{
+		# We need this information about the current last comment line
+		if (footerComment == 2) {
+			footerComment = 0
 		}
-		splice(@footer, $line, 0, "Change-Id: I$id");
+		if (lines != "") {
+			lines = lines "\n";
+		}
+		lines = lines $0
+	}
 
-		$_ = join("\n", @message, @footer);
-		open(O, ">$MSG"); print O; close O;
-	' "$MSG" "$id" "$CHANGE_ID_AFTER"
+	# Footer handling:
+	# If the last block is considered a footer, splice in the Change-Id at the
+	# right place.
+	# Look for the right place to inject Change-Id by considering
+	# CHANGE_ID_AFTER. Keys listed in it (case insensitive) come first,
+	# then Change-Id, then everything else (eg. Signed-off-by:).
+	#
+	# Otherwise just print the last block, a new line and the Change-Id as a
+	# block of its own.
+	END {
+		unprinted = 1
+		if (isFooter == 0) {
+			print lines "\n"
+			lines = ""
+		}
+		changeIdAfter = "^(" tolower("'"$CHANGE_ID_AFTER"'") "):"
+		numlines = split(lines, footer, "\n")
+		for (line = 1; line <= numlines; line++) {
+			if (unprinted && match(tolower(footer[line]), changeIdAfter) != 1) {
+				unprinted = 0
+				print "Change-Id: I'"$id"'"
+			}
+			print footer[line]
+		}
+		if (unprinted) {
+			print "Change-Id: I'"$id"'"
+		}
+	}' "$MSG" > $T && mv $T "$MSG" || rm -f $T
 }
 _gen_ChangeIdInput() {
-	echo "tree $(git write-tree)"
-	if parent=$(git rev-parse HEAD^0 2>/dev/null)
+	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 $(git var GIT_COMMITTER_IDENT)"
+	echo "author `git var GIT_AUTHOR_IDENT`"
+	echo "committer `git var GIT_COMMITTER_IDENT`"
 	echo
 	printf '%s' "$clean_message"
 }