[PATCH 12/13] path-walk: add new 'edge_aggressive' option

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <stolee@gmail.com>

In preparation for allowing both the --shallow and --path-walk options
in the 'git pack-objects' builtin, create a new 'edge_aggressive' option
in the path-walk API. This option will help walk the boundary more
thoroughly and help avoid sending extra objects during fetches and
pushes.

The only use of the 'edge_hint_aggressive' option in the revision API is
within mark_edges_uninteresting(), which is usually called before
between prepare_revision_walk() and before visiting commits with
get_revision(). In prepare_revision_walk(), the UNINTERESTING commits
are walked until a boundary is found.

Signed-off-by: Derrick Stolee <stolee@gmail.com>
---
 Documentation/technical/api-path-walk.adoc |  8 ++++++++
 path-walk.c                                |  6 +++++-
 path-walk.h                                |  7 +++++++
 t/helper/test-path-walk.c                  |  2 ++
 t/t6601-path-walk.sh                       | 20 ++++++++++++++++++++
 5 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/Documentation/technical/api-path-walk.adoc b/Documentation/technical/api-path-walk.adoc
index e522695dd9f..34c905eb9c3 100644
--- a/Documentation/technical/api-path-walk.adoc
+++ b/Documentation/technical/api-path-walk.adoc
@@ -56,6 +56,14 @@ better off using the revision walk API instead.
 	the revision walk so that the walk emits commits marked with the
 	`UNINTERESTING` flag.
 
+`edge_aggressive`::
+	For performance reasons, usually only the boundary commits are
+	explored to find UNINTERESTING objects. However, in the case of
+	shallow clones it can be helpful to mark all trees and blobs
+	reachable from UNINTERESTING tip commits as UNINTERESTING. This
+	matches the behavior of `--objects-edge-aggressive` in the
+	revision API.
+
 `pl`::
 	This pattern list pointer allows focusing the path-walk search to
 	a set of patterns, only emitting paths that match the given
diff --git a/path-walk.c b/path-walk.c
index 341bdd2ba4e..2d4ddbadd50 100644
--- a/path-walk.c
+++ b/path-walk.c
@@ -503,7 +503,11 @@ int walk_objects_by_path(struct path_walk_info *info)
 	if (prepare_revision_walk(info->revs))
 		die(_("failed to setup revision walk"));
 
-	/* Walk trees to mark them as UNINTERESTING. */
+	/*
+	 * Walk trees to mark them as UNINTERESTING.
+	 * This is particularly important when 'edge_aggressive' is set.
+	 */
+	info->revs->edge_hint_aggressive = info->edge_aggressive;
 	edge_repo = info->revs->repo;
 	edge_tree_list = root_tree_list;
 	mark_edges_uninteresting(info->revs, show_edge,
diff --git a/path-walk.h b/path-walk.h
index 473ee9d361c..5ef5a8440e6 100644
--- a/path-walk.h
+++ b/path-walk.h
@@ -50,6 +50,13 @@ struct path_walk_info {
 	 */
 	int prune_all_uninteresting;
 
+	/**
+	 * When 'edge_aggressive' is set, then the revision walk will use
+	 * the '--object-edge-aggressive' option to mark even more objects
+	 * as uninteresting.
+	 */
+	int edge_aggressive;
+
 	/**
 	 * Specify a sparse-checkout definition to match our paths to. Do not
 	 * walk outside of this sparse definition. If the patterns are in
diff --git a/t/helper/test-path-walk.c b/t/helper/test-path-walk.c
index 61e845e5ec2..fe63002c2be 100644
--- a/t/helper/test-path-walk.c
+++ b/t/helper/test-path-walk.c
@@ -82,6 +82,8 @@ int cmd__path_walk(int argc, const char **argv)
 			 N_("toggle inclusion of tree objects")),
 		OPT_BOOL(0, "prune", &info.prune_all_uninteresting,
 			 N_("toggle pruning of uninteresting paths")),
+		OPT_BOOL(0, "edge-aggressive", &info.edge_aggressive,
+			 N_("toggle aggressive edge walk")),
 		OPT_BOOL(0, "stdin-pl", &stdin_pl,
 			 N_("read a pattern list over stdin")),
 		OPT_END(),
diff --git a/t/t6601-path-walk.sh b/t/t6601-path-walk.sh
index c89b0f1e19d..785c2f22373 100755
--- a/t/t6601-path-walk.sh
+++ b/t/t6601-path-walk.sh
@@ -378,6 +378,26 @@ test_expect_success 'topic, not base, boundary with pruning' '
 	test_cmp_sorted expect out
 '
 
+test_expect_success 'topic, not base, --edge-aggressive with pruning' '
+	test-tool path-walk --prune --edge-aggressive -- topic --not base >out &&
+
+	cat >expect <<-EOF &&
+	0:commit::$(git rev-parse topic)
+	1:tree::$(git rev-parse topic^{tree})
+	1:tree::$(git rev-parse base^{tree}):UNINTERESTING
+	2:tree:right/:$(git rev-parse topic:right)
+	2:tree:right/:$(git rev-parse base:right):UNINTERESTING
+	3:blob:right/c:$(git rev-parse base:right/c):UNINTERESTING
+	3:blob:right/c:$(git rev-parse topic:right/c)
+	blobs:2
+	commits:1
+	tags:0
+	trees:4
+	EOF
+
+	test_cmp_sorted expect out
+'
+
 test_expect_success 'trees are reported exactly once' '
 	test_when_finished "rm -rf unique-trees" &&
 	test_create_repo unique-trees &&
-- 
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