Merge branch 'sg/t9300-robustify'

The test on "fast-import" used to get stuck when "fast-import" died
in the middle.

* sg/t9300-robustify:
  t9300-fast-import: don't hang if background fast-import exits too early
  t9300-fast-import: store the PID in a variable instead of pidfile

t/t9300-fast-import.sh

@@ -3191,13 +3191,22 @@ background_import_then_checkpoint () {
 	exec 9<>V.output
 	rm V.output
 
+	(
 		git fast-import $options <&8 >&9 &
-	echo $! >V.pid
+		echo $! >&9
+		wait $!
+		echo >&2 "background fast-import terminated too early with exit code $?"
+		# Un-block the read loop in the main shell process.
+		echo >&9 UNEXPECTED
+	) &
+	sh_pid=$!
+	read fi_pid <&9
 	# We don't mind if fast-import has already died by the time the test
 	# ends.
 	test_when_finished "
 		exec 8>&-; exec 9>&-;
-		kill $(cat V.pid) && wait $(cat V.pid)
+		kill $sh_pid && wait $sh_pid
+		kill $fi_pid && wait $fi_pid
 		true"
 
 	# Start in the background to ensure we adhere strictly to (blocking)
@@ -3217,6 +3226,9 @@ background_import_then_checkpoint () {
 		then
 			error=0
 			break
+		elif test "$output" = "UNEXPECTED"
+		then
+			break
 		fi
 		# otherwise ignore cruft
 		echo >&2 "cruft: $output"
@@ -3229,7 +3241,7 @@ background_import_then_checkpoint () {
 }
 
 background_import_still_running () {
-	if ! kill -0 "$(cat V.pid)"
+	if ! kill -0 "$fi_pid"
 	then
 		echo >&2 "background fast-import terminated too early"
 		false