1 files changed, 67 insertions, 2 deletions

diff --git a/builtin-fetch.c b/builtin-fetch.c
index 1cb30c52c..c1930aaa0 100644
--- a/builtin-fetch.c
+++ b/builtin-fetch.c
@@ -8,10 +8,12 @@
 #include "path-list.h"
 #include "remote.h"
 #include "transport.h"
+#include "run-command.h"
 
 static const char fetch_usage[] = "git-fetch [-a | --append] [--upload-pack <upload-pack>] [-f | --force] [--no-tags] [-t | --tags] [-k | --keep] [-u | --update-head-ok] [--depth <depth>] [-v | --verbose] [<repository> <refspec>...]";
 
 static int append, force, tags, no_tags, update_head_ok, verbose, quiet;
+static const char *depth;
 static char *default_rla = NULL;
 static struct transport *transport;
 
@@ -330,9 +332,72 @@ static void store_updated_refs(const char *url, struct ref *ref_map)
 	fclose(fp);
 }
 
+/*
+ * We would want to bypass the object transfer altogether if
+ * everything we are going to fetch already exists and connected
+ * locally.
+ *
+ * The refs we are going to fetch are in to_fetch (nr_heads in
+ * total).  If running
+ *
+ *  $ git-rev-list --objects to_fetch[0] to_fetch[1] ... --not --all
+ *
+ * does not error out, that means everything reachable from the
+ * refs we are going to fetch exists and is connected to some of
+ * our existing refs.
+ */
+static int quickfetch(struct ref *ref_map)
+{
+	struct child_process revlist;
+	struct ref *ref;
+	char **argv;
+	int i, err;
+
+	/*
+	 * If we are deepening a shallow clone we already have these
+	 * objects reachable.  Running rev-list here will return with
+	 * a good (0) exit status and we'll bypass the fetch that we
+	 * really need to perform.  Claiming failure now will ensure
+	 * we perform the network exchange to deepen our history.
+	 */
+	if (depth)
+		return -1;
+
+	for (i = 0, ref = ref_map; ref; ref = ref->next)
+		i++;
+	if (!i)
+		return 0;
+
+	argv = xmalloc(sizeof(*argv) * (i + 6));
+	i = 0;
+	argv[i++] = xstrdup("rev-list");
+	argv[i++] = xstrdup("--quiet");
+	argv[i++] = xstrdup("--objects");
+	for (ref = ref_map; ref; ref = ref->next)
+		argv[i++] = xstrdup(sha1_to_hex(ref->old_sha1));
+	argv[i++] = xstrdup("--not");
+	argv[i++] = xstrdup("--all");
+	argv[i++] = NULL;
+
+	memset(&revlist, 0, sizeof(revlist));
+	revlist.argv = (const char**)argv;
+	revlist.git_cmd = 1;
+	revlist.no_stdin = 1;
+	revlist.no_stdout = 1;
+	revlist.no_stderr = 1;
+	err = run_command(&revlist);
+
+	for (i = 0; argv[i]; i++)
+		free(argv[i]);
+	free(argv);
+	return err;
+}
+
 static int fetch_refs(struct transport *transport, struct ref *ref_map)
 {
-	int ret = transport_fetch_refs(transport, ref_map);
+	int ret = quickfetch(ref_map);
+	if (ret)
+		ret = transport_fetch_refs(transport, ref_map);
 	if (!ret)
 		store_updated_refs(transport->url, ref_map);
 	transport_unlock_pack(transport);
@@ -468,7 +533,7 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 	static const char **refs = NULL;
 	int ref_nr = 0;
 	int cmd_len = 0;
-	const char *depth = NULL, *upload_pack = NULL;
+	const char *upload_pack = NULL;
 	int keep = 0;
 
 	for (i = 1; i < argc; i++) {