gvfs-helper-client: clean up server process

On Linux, the following command would cause the terminal to be stuck
waiting:

  git fetch origin foobar

The issue would be that the fetch would fail with the error

  fatal: couldn't find remote ref foobar

but the underlying git-gvfs-helper process wouldn't die. The
subprocess_exit_handler() method would close its stdin and stdout, but
that wouldn't be enough to cause the process to end.

The current appraoch creates our own atexit() handler by sending a
SIGINT signal to the child process. This has worked in my end-to-end
test.

Perhaps another approach would be to investigate why the git-gvfs-helper
server does not terminate when its stdin closes.

Reported-by: Stuart Wilcox Humilde <[email protected]>
Signed-off-by: Derrick Stolee <[email protected]>

Author: derrickstolee

gvfs-helper-client.c

@@ -38,6 +38,16 @@ static struct object_directory *gh_client__chosen_odb;
 #define CAP_OBJECTS__VERB_POST_NAME "post"
 #define CAP_OBJECTS__VERB_PREFETCH_NAME "prefetch"
 
+static int server_process_pid = 0;
+
+static void cleanup_server_process_on_exit(void)
+{
+	if (server_process_pid) {
+		kill(server_process_pid, SIGINT);
+		server_process_pid = 0;
+	}
+}
+
 static int gh_client__start_fn(struct subprocess_entry *subprocess)
 {
 	static int versions[] = {1, 0};
@@ -48,6 +58,8 @@ static int gh_client__start_fn(struct subprocess_entry *subprocess)
 
 	struct gh_server__process *entry = (struct gh_server__process *)subprocess;
 
+	server_process_pid = subprocess->process.pid;
+	atexit(cleanup_server_process_on_exit);
 	return subprocess_handshake(subprocess, "gvfs-helper", versions,
 				    NULL, capabilities,
 				    &entry->supported_capabilities);