git-daemon tests: wait until daemon is ready

In start_daemon, git-daemon is started as a background process.  In
theory, the tests may try to connect before the daemon had a chance
to open a listening socket. Avoid this race condition by waiting
for it to output "Ready to rumble". Any other output is considered
an error and the test is aborted.

Should git-daemon produce no output at all, lib-git-daemon would
block forever. This could be fixed by introducing a timeout.  On
the other hand, we have no timeout for other git commands which
could suffer from the same problem. Since such a mechanism adds
some complexity, I have decided against it.

Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Clemens Buchacher

t/lib-git-daemon.sh

@@ -23,12 +23,27 @@ start_git_daemon() {
 	trap 'code=$?; stop_git_daemon; (exit $code); die' EXIT
 
 	say >&3 "Starting git daemon ..."
+	mkfifo git_daemon_output
 	git daemon --listen=127.0.0.1 --port="$LIB_GIT_DAEMON_PORT" \
 		--reuseaddr --verbose \
 		--base-path="$GIT_DAEMON_DOCUMENT_ROOT_PATH" \
 		"$@" "$GIT_DAEMON_DOCUMENT_ROOT_PATH" \
-		>&3 2>&4 &
+		>&3 2>git_daemon_output &
 	GIT_DAEMON_PID=$!
+	{
+		read line
+		echo >&4 "$line"
+		cat >&4 &
+
+		# Check expected output
+		if test x"$(expr "$line" : "\[[0-9]*\] \(.*\)")" != x"Ready to rumble"
+		then
+			kill "$GIT_DAEMON_PID"
+			wait "$GIT_DAEMON_PID"
+			trap 'die' EXIT
+			error "git daemon failed to start"
+		fi
+	} <git_daemon_output
 }
 
 stop_git_daemon() {
@@ -50,4 +65,5 @@ stop_git_daemon() {
 		error "git daemon exited with status: $ret"
 	fi
 	GIT_DAEMON_PID=
+	rm -f git_daemon_output
 }