git-daemon: use 'test_atexit` to stop 'git-daemon'

Use 'test_atexit' to run cleanup commands to stop 'git-daemon' at the
end of the test script or upon interrupt or failure, as it is shorter,
simpler, and more robust than registering such cleanup commands in the
trap on EXIT in the test scripts.

Note that in 't5570-git-daemon.sh' the daemon is stopped and then
re-started in the middle of the test script; take care that the
cleanup functions to stop the daemon are only registered once.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/interop/i5500-git-daemon.sh

@@ -37,5 +37,4 @@ test_expect_success "fetch with $VERSION_B" '
 	test_cmp expect actual
 '
 
-stop_git_daemon
 test_done

t/lib-git-daemon.sh

@@ -13,7 +13,6 @@
 #
 #	test_expect_success ...
 #
-#	stop_git_daemon
 #	test_done
 
 test_tristate GIT_TEST_GIT_DAEMON
@@ -36,6 +35,7 @@ GIT_DAEMON_DOCUMENT_ROOT_PATH="$PWD"/repo
 GIT_DAEMON_HOST_PORT=127.0.0.1:$LIB_GIT_DAEMON_PORT
 GIT_DAEMON_URL=git://$GIT_DAEMON_HOST_PORT
 
+registered_stop_git_daemon_atexit_handler=
 start_git_daemon() {
 	if test -n "$GIT_DAEMON_PID"
 	then
@@ -44,7 +44,13 @@ start_git_daemon() {
 
 	mkdir -p "$GIT_DAEMON_DOCUMENT_ROOT_PATH"
 
-	trap 'code=$?; stop_git_daemon; (exit $code); die' EXIT
+	# One of the test scripts stops and then re-starts 'git daemon'.
+	# Don't register and then run the same atexit handlers several times.
+	if test -z "$registered_stop_git_daemon_atexit_handler"
+	then
+		test_atexit 'stop_git_daemon'
+		registered_stop_git_daemon_atexit_handler=AlreadyDone
+	fi
 
 	say >&3 "Starting git daemon ..."
 	mkfifo git_daemon_output
@@ -66,7 +72,7 @@ start_git_daemon() {
 	then
 		kill "$GIT_DAEMON_PID"
 		wait "$GIT_DAEMON_PID"
-		trap 'die' EXIT
+		unset GIT_DAEMON_PID
 		test_skip_or_die $GIT_TEST_GIT_DAEMON \
 			"git daemon failed to start"
 	fi
@@ -78,8 +84,6 @@ stop_git_daemon() {
 		return
 	fi
 
-	trap 'die' EXIT
-
 	# kill git-daemon child of git
 	say >&3 "Stopping git daemon ..."
 	kill "$GIT_DAEMON_PID"

t/t5570-git-daemon.sh

@@ -198,5 +198,4 @@ test_expect_success FAKENC 'hostname interpolation works after LF-stripping' '
 	test_cmp expect actual
 '
 
-stop_git_daemon
 test_done