Merge branch 'sg/test-atexit'

Test framework update to more robustly clean up leftover files and
processes after tests are done.

* sg/test-atexit:
  t9811-git-p4-label-import: fix pipeline negation
  git p4 test: disable '-x' tracing in the p4d watchdog loop
  git p4 test: simplify timeout handling
  git p4 test: clean up the p4d cleanup functions
  git p4 test: use 'test_atexit' to kill p4d and the watchdog process
  t0301-credential-cache: use 'test_atexit' to stop the credentials helper
  tests: use 'test_atexit' to stop httpd
  git-daemon: use 'test_atexit` to stop 'git-daemon'
  test-lib: introduce 'test_atexit'
  t/lib-git-daemon: make sure to kill the 'git-daemon' process
  test-lib: fix interrupt handling with 'dash' and '--verbose-log -x'

t/test-lib-functions.sh

@@ -943,6 +943,34 @@ test_when_finished () {
 		} && (exit \"\$eval_ret\"); eval_ret=\$?; $test_cleanup"
 }
 
+# This function can be used to schedule some commands to be run
+# unconditionally at the end of the test script, e.g. to stop a daemon:
+#
+#	test_expect_success 'test git daemon' '
+#		git daemon &
+#		daemon_pid=$! &&
+#		test_atexit 'kill $daemon_pid' &&
+#		hello world
+#	'
+#
+# The commands will be executed before the trash directory is removed,
+# i.e. the atexit commands will still be able to access any pidfiles or
+# socket files.
+#
+# Note that these commands will be run even when a test script run
+# with '--immediate' fails.  Be careful with your atexit commands to
+# minimize any changes to the failed state.
+
+test_atexit () {
+	# We cannot detect when we are in a subshell in general, but by
+	# doing so on Bash is better than nothing (the test will
+	# silently pass on other shells).
+	test "${BASH_SUBSHELL-0}" = 0 ||
+	error "bug in test script: test_atexit does nothing in a subshell"
+	test_atexit_cleanup="{ $*
+		} && (exit \"\$eval_ret\"); eval_ret=\$?; $test_atexit_cleanup"
+}
+
 # Most tests can use the created repository, but some may need to create more.
 # Usage: test_create_repo <directory>
 test_create_repo () {