[PATCH 03/10] builtin/pack-objects.c: learn '--assume-kept-packs-closed'

@@ -135,6 +135,17 @@ depth is 4095.
 	leading directory (e.g. `pack-123.pack`). The option could be
 	specified multiple times to keep multiple packs.
 
+--assume-kept-packs-closed::
+	This flag causes `git rev-list` to halt the object traversal
+	when it encounters an object found in a kept pack. This is
+	dissimilar to `--honor-pack-keep`, which only prunes unwanted
+	results after the full traversal is completed.
++
+Without any `--keep-pack=<pack-name>` arguments, only packs with an
+on-disk `*.keep` files are used when considering when to halt the
+traversal. If other packs are artificially marked as "kept" with
+`--keep-pack`, then those are considered as well.
+
 --incremental::
 	This flag causes an object already in a pack to be ignored
 	even if it would have otherwise been packed.

@@ -78,6 +78,7 @@ static int have_non_local_packs;
 static int incremental;
 static int ignore_packed_keep_on_disk;
 static int ignore_packed_keep_in_core;
+static int assume_kept_packs_closed;
 static int allow_ofs_delta;
 static struct pack_idx_option pack_idx_opts;
 static const char *base_name;

@@ -3542,6 +3543,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 			 N_("create packs suitable for shallow fetches")),
 		OPT_BOOL(0, "honor-pack-keep", &ignore_packed_keep_on_disk,
 			 N_("ignore packs that have companion .keep file")),
+		OPT_BOOL(0, "assume-kept-packs-closed", &assume_kept_packs_closed,
+			 N_("assume the union of kept packs is closed under reachability")),
 		OPT_STRING_LIST(0, "keep-pack", &keep_pack_list, N_("name"),
 				N_("ignore this pack")),
 		OPT_INTEGER(0, "compression", &pack_compression_level,

@@ -3631,6 +3634,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 		use_internal_rev_list = 1;
 		strvec_push(&rp, "--unpacked");
 	}
+	if (assume_kept_packs_closed)
+		use_internal_rev_list = 1;
 
 	if (exclude_promisor_objects) {
 		use_internal_rev_list = 1;

@@ -3711,6 +3716,14 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 		if (!p) /* no keep-able packs found */
 			ignore_packed_keep_on_disk = 0;
 	}
+	if (assume_kept_packs_closed) {
+		if (ignore_packed_keep_on_disk && ignore_packed_keep_in_core)
+			strvec_push(&rp, "--no-kept-objects");
+		else if (ignore_packed_keep_on_disk)
+			strvec_push(&rp, "--no-kept-objects=on-disk");
+		else if (ignore_packed_keep_in_core)
+			strvec_push(&rp, "--no-kept-objects=in-core");
+	}
 	if (local) {
 		/*
 		 * unlike ignore_packed_keep_on_disk above, we do not

@@ -66,4 +66,63 @@ test_expect_success '--no-kept-objects excludes kept non-MIDX object' '
 	test_cmp expect actual
 '
 
+test_expect_success '--no-kept-objects can respect only in-core keep packs' '
+	test_when_finished "rm -fr actual-*.idx actual-*.pack" &&
+	(
+		git rev-list --objects --no-object-names packed..kept &&
+		git rev-list --objects --no-object-names loose
+	) | sort >expect &&
+
+	git pack-objects \
+	  --assume-kept-packs-closed \
+	  --keep-pack=pack-$MISC_PACK.pack \
+	  --all actual </dev/null &&
+	idx_objects actual-*.idx >actual &&
+
+	test_cmp expect actual
+'
+
+test_expect_success 'setup additional --no-kept-objects tests' '
+	test_commit additional &&
+
+	ADDITIONAL_PACK=$(git pack-objects --revs .git/objects/pack/pack <<-EOF
+	refs/tags/additional
+	^refs/tags/kept
+	EOF
+	)
+'
+
+test_expect_success '--no-kept-objects can respect only on-disk keep packs' '
+	test_when_finished "rm -fr actual-*.idx actual-*.pack" &&
+	(
+		git rev-list --objects --no-object-names kept..additional &&
+		git rev-list --objects --no-object-names packed
+	) | sort >expect &&
+
+	git pack-objects \
+	  --assume-kept-packs-closed \
+	  --honor-pack-keep \
+	  --all actual </dev/null &&
+	idx_objects actual-*.idx >actual &&
+
+	test_cmp expect actual
+'
+
+test_expect_success '--no-kept-objects can respect mixed kept packs' '
+	test_when_finished "rm -fr actual-*.idx actual-*.pack" &&
+	(
+		git rev-list --objects --no-object-names kept..additional &&
+		git rev-list --objects --no-object-names loose
+	) | sort >expect &&
+
+	git pack-objects \
+	  --assume-kept-packs-closed \
+	  --honor-pack-keep \
+	  --keep-pack=pack-$MISC_PACK.pack \
+	  --all actual </dev/null &&
+	idx_objects actual-*.idx >actual &&
+
+	test_cmp expect actual
+'
+
 test_done