pack-objects: use --objects-edge-aggressive for shallow repos

When fetching into or pushing from a shallow repository, we want to
aggressively mark edges as uninteresting, since this decreases the pack
size.  However, aggressively marking edges can negatively affect
performance on large non-shallow repositories with lots of refs.

Teach pack-objects a --shallow option to indicate that we're pushing
from or fetching into a shallow repository.  Use
--objects-edge-aggressive only for shallow repositories and otherwise
use --objects-edge, which performs better in the general case.  Update
the callers to pass the --shallow option when they are dealing with a
shallow repository.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-pack-objects.txt

@@ -13,7 +13,7 @@ SYNOPSIS
 	[--no-reuse-delta] [--delta-base-offset] [--non-empty]
 	[--local] [--incremental] [--window=<n>] [--depth=<n>]
 	[--revs [--unpacked | --all]] [--stdout | base-name]
-	[--keep-true-parents] < object-list
+	[--shallow] [--keep-true-parents] < object-list
 
 
 DESCRIPTION
@@ -190,6 +190,11 @@ required objects and is thus unusable by Git without making it
 self-contained. Use `git index-pack --fix-thin`
 (see linkgit:git-index-pack[1]) to restore the self-contained property.
 
+--shallow::
+	Optimize a pack that will be provided to a client with a shallow
+	repository.  This option, combined with \--thin, can result in a
+	smaller pack at the cost of speed.
+
 --delta-base-offset::
 	A packed archive can express the base object of a delta as
 	either a 20-byte object name or as an offset in the

Documentation/rev-list-options.txt

@@ -659,7 +659,8 @@ These options are mostly targeted for packing of Git repositories.
 
 --objects-edge-aggressive::
 	Similar to `--objects-edge`, but it tries harder to find excluded
-	commits at the cost of increased time.
+	commits at the cost of increased time.  This is used instead of
+	`--objects-edge` to build ``thin'' packs for shallow repositories.
 
 --unpacked::
 	Only useful with `--objects`; print the object IDs that are not

builtin/pack-objects.c

@@ -2613,6 +2613,7 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 {
 	int use_internal_rev_list = 0;
 	int thin = 0;
+	int shallow = 0;
 	int all_progress_implied = 0;
 	struct argv_array rp = ARGV_ARRAY_INIT;
 	int rev_list_unpacked = 0, rev_list_all = 0, rev_list_reflog = 0;
@@ -2677,6 +2678,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 		  PARSE_OPT_OPTARG, option_parse_unpack_unreachable },
 		OPT_BOOL(0, "thin", &thin,
 			 N_("create thin packs")),
+		OPT_BOOL(0, "shallow", &shallow,
+			 N_("create packs suitable for shallow fetches")),
 		OPT_BOOL(0, "honor-pack-keep", &ignore_packed_keep,
 			 N_("ignore packs that have companion .keep file")),
 		OPT_INTEGER(0, "compression", &pack_compression_level,
@@ -2711,7 +2714,9 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 	argv_array_push(&rp, "pack-objects");
 	if (thin) {
 		use_internal_rev_list = 1;
-		argv_array_push(&rp, "--objects-edge-aggressive");
+		argv_array_push(&rp, shallow
+				? "--objects-edge-aggressive"
+				: "--objects-edge");
 	} else
 		argv_array_push(&rp, "--objects");
 

send-pack.c

@@ -47,6 +47,7 @@ static int pack_objects(int fd, struct ref *refs, struct sha1_array *extra, stru
 		NULL,
 		NULL,
 		NULL,
+		NULL,
 	};
 	struct child_process po = CHILD_PROCESS_INIT;
 	int i;
@@ -60,6 +61,8 @@ static int pack_objects(int fd, struct ref *refs, struct sha1_array *extra, stru
 		argv[i++] = "-q";
 	if (args->progress)
 		argv[i++] = "--progress";
+	if (is_repository_shallow())
+		argv[i++] = "--shallow";
 	po.argv = argv;
 	po.in = -1;
 	po.out = args->stateless_rpc ? -1 : fd;

upload-pack.c

@@ -86,7 +86,7 @@ static void create_pack_file(void)
 		"corruption on the remote side.";
 	int buffered = -1;
 	ssize_t sz;
-	const char *argv[12];
+	const char *argv[13];
 	int i, arg = 0;
 	FILE *pipe_fd;
 
@@ -100,6 +100,8 @@ static void create_pack_file(void)
 		argv[arg++] = "--thin";
 
 	argv[arg++] = "--stdout";
+	if (shallow_nr)
+		argv[arg++] = "--shallow";
 	if (!no_progress)
 		argv[arg++] = "--progress";
 	if (use_ofs_delta)