fsmonitor--daemon: background daemon must free the console on windows

Teach "git fsmonitor--daemon run" to call FreeConsole() when started
in the background by "git fsmonitor--daemon start" on Windows.

The background process was holding a handle to the inherited Win32
console despite being passed stdin/out/err set to /dev/null.  This
caused command prompts and powershell terminal windows to hang in
"exit" waiting for the last console handle to be released.

(This problem was not seen in git-bash type terminal windows because
they don't have a Win32 console attached to them.)

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>

builtin/fsmonitor--daemon.c

@@ -1302,7 +1302,7 @@ static int fsmonitor_run_daemon(void)
 	return err;
 }
 
-static int try_to_run_foreground_daemon(void)
+static int try_to_run_foreground_daemon(int free_console)
 {
 	/*
 	 * Technically, we don't need to probe for an existing daemon
@@ -1320,6 +1320,11 @@ static int try_to_run_foreground_daemon(void)
 	       the_repository->worktree);
 	fflush(stdout);
 
+#ifdef GIT_WINDOWS_NATIVE
+	if (free_console)
+		FreeConsole();
+#endif
+
 	return !!fsmonitor_run_daemon();
 }
 
@@ -1351,6 +1356,7 @@ static int spawn_fsmonitor(pid_t *pid)
 	strvec_push(&args, git_exe);
 	strvec_push(&args, "fsmonitor--daemon");
 	strvec_push(&args, "run");
+	strvec_push(&args, "--free-console");
 	strvec_pushf(&args, "--ipc-threads=%d", fsmonitor__ipc_threads);
 
 	*pid = mingw_spawnvpe(args.v[0], args.v, NULL, NULL, in, out, out);
@@ -1514,8 +1520,10 @@ static int try_to_start_background_daemon(void)
 int cmd_fsmonitor__daemon(int argc, const char **argv, const char *prefix)
 {
 	const char *subcmd;
+	int free_console = 0;
 
 	struct option options[] = {
+		OPT_BOOL(0, "free-console", &free_console, N_("free console")),
 		OPT_INTEGER(0, "ipc-threads",
 			    &fsmonitor__ipc_threads,
 			    N_("use <n> ipc worker threads")),
@@ -1559,7 +1567,7 @@ int cmd_fsmonitor__daemon(int argc, const char **argv, const char *prefix)
 		return !!try_to_start_background_daemon();
 
 	if (!strcmp(subcmd, "run"))
-		return !!try_to_run_foreground_daemon();
+		return !!try_to_run_foreground_daemon(free_console);
 
 	if (!strcmp(subcmd, "stop"))
 		return !!do_as_client__send_stop();