rev-list: add an option to mark fewer edges as uninteresting

In commit fbd4a70 (list-objects: mark more commits as edges in
mark_edges_uninteresting - 2013-08-16), we marked an increasing number
of edges uninteresting.  This change, and the subsequent change to make
this conditional on --objects-edge, are used by --thin to make much
smaller packs for shallow clones.

Unfortunately, they cause a significant performance regression when
pushing non-shallow clones with lots of refs (23.322 seconds vs.
4.785 seconds with 22400 refs).  Add an option to git rev-list,
--objects-edge-aggressive, that preserves this more aggressive behavior,
while leaving --objects-edge to provide more performant behavior.
Preserve the current behavior for the moment by using the aggressive
option.

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

Documentation/git-rev-list.txt

@@ -46,7 +46,8 @@ SYNOPSIS
 	     [ \--extended-regexp | -E ]
 	     [ \--fixed-strings | -F ]
 	     [ \--date=(local|relative|default|iso|iso-strict|rfc|short) ]
-	     [ [\--objects | \--objects-edge] [ \--unpacked ] ]
+	     [ [ \--objects | \--objects-edge | \--objects-edge-aggressive ]
+	       [ \--unpacked ] ]
 	     [ \--pretty | \--header ]
 	     [ \--bisect ]
 	     [ \--bisect-vars ]

Documentation/rev-list-options.txt

@@ -657,6 +657,10 @@ These options are mostly targeted for packing of Git repositories.
 	objects in deltified form based on objects contained in these
 	excluded commits to reduce network traffic.
 
+--objects-edge-aggressive::
+	Similar to `--objects-edge`, but it tries harder to find excluded
+	commits at the cost of increased time.
+
 --unpacked::
 	Only useful with `--objects`; print the object IDs that are not
 	in packs.

builtin/pack-objects.c

@@ -2711,7 +2711,7 @@ 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");
+		argv_array_push(&rp, "--objects-edge-aggressive");
 	} else
 		argv_array_push(&rp, "--objects");
 

list-objects.c

@@ -157,7 +157,7 @@ void mark_edges_uninteresting(struct rev_info *revs, show_edge_fn show_edge)
 
 		if (commit->object.flags & UNINTERESTING) {
 			mark_tree_uninteresting(commit->tree);
-			if (revs->edge_hint && !(commit->object.flags & SHOWN)) {
+			if (revs->edge_hint_aggressive && !(commit->object.flags & SHOWN)) {
 				commit->object.flags |= SHOWN;
 				show_edge(commit);
 			}
@@ -165,7 +165,7 @@ void mark_edges_uninteresting(struct rev_info *revs, show_edge_fn show_edge)
 		}
 		mark_edge_parents_uninteresting(commit, revs, show_edge);
 	}
-	if (revs->edge_hint) {
+	if (revs->edge_hint_aggressive) {
 		for (i = 0; i < revs->cmdline.nr; i++) {
 			struct object *obj = revs->cmdline.rev[i].item;
 			struct commit *commit = (struct commit *)obj;

revision.c

@@ -1853,6 +1853,12 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->tree_objects = 1;
 		revs->blob_objects = 1;
 		revs->edge_hint = 1;
+	} else if (!strcmp(arg, "--objects-edge-aggressive")) {
+		revs->tag_objects = 1;
+		revs->tree_objects = 1;
+		revs->blob_objects = 1;
+		revs->edge_hint = 1;
+		revs->edge_hint_aggressive = 1;
 	} else if (!strcmp(arg, "--verify-objects")) {
 		revs->tag_objects = 1;
 		revs->tree_objects = 1;

revision.h

@@ -93,6 +93,7 @@ struct rev_info {
 			blob_objects:1,
 			verify_objects:1,
 			edge_hint:1,
+			edge_hint_aggressive:1,
 			limited:1,
 			unpacked:1,
 			boundary:2,