Always ensure the pack.keep file is removed by git-fetch

If we are using a native transport and the transport chose to
save the packfile it may have created a .keep file to protect
the packfile from a concurrently running git-repack process.

In such a case the git-fetch process should make sure it will
unlink the .keep file even if it fails to update any refs as
otherwise the newly downloaded packfile's diskspace will never
be reclaimed if the objects are not actually referenced.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-fetch.c

@@ -13,6 +13,20 @@ static const char fetch_usage[] = "git-fetch [-a | --append] [--upload-pack <upl
 
 static int append, force, tags, no_tags, update_head_ok, verbose, quiet;
 static char *default_rla = NULL;
+static struct transport *transport;
+
+static void unlock_pack(void)
+{
+	if (transport)
+		transport_unlock_pack(transport);
+}
+
+static void unlock_pack_on_signal(int signo)
+{
+	unlock_pack();
+	signal(SIGINT, SIG_DFL);
+	raise(signo);
+}
 
 static void find_merge_config(struct ref *ref_map, struct remote *remote)
 {
@@ -396,7 +410,6 @@ static int do_fetch(struct transport *transport,
 int cmd_fetch(int argc, const char **argv, const char *prefix)
 {
 	struct remote *remote;
-	struct transport *transport;
 	int i, j, rla_offset;
 	static const char **refs = NULL;
 	int ref_nr = 0;
@@ -520,5 +533,7 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 			printf("ref: %s\n", refs[j]);
 	}
 
+	signal(SIGINT, unlock_pack_on_signal);
+	atexit(unlock_pack);
 	return do_fetch(transport, parse_ref_spec(ref_nr, refs), ref_nr);
 }