[PATCH 5/7] merge-ort: defer recursing into directories when merge base is matched

["Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>]

From: Elijah Newren <newren@gmail.com>

When one side of history matches the merge base (including when the
merge base has no entry for the given directory), have
collect_merge_info_callback() defer recursing into the directory.  To
ensure those entries are eventually handled, add a call to
handled_deferred_entries() in collect_merge_info() after
traverse_trees() returns.

Note that the condition in collect_merge_info_callback() may look more
complicated than necessary at first glance;
renames->trivial_merges_okay[side] is always true until
handle_deferred_entries() is called, and possible_trivial_merges[side]
is always empty right now (and in the future won't be filled until
handle_deferred_entries() is called).  However, when
handle_deferred_entries() calls traverse_trees() for the relevant
deferred directories, those traverse_trees() calls will once again end
up in collect_merge_info_callback() for all the entries under those
subdirectories.  The extra conditions are there for such deferred cases
and will be used more as we do more with those variables.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 merge-ort.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/merge-ort.c b/merge-ort.c
index eb0e18d7546..bf0712d18a0 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -1141,8 +1141,35 @@ static int collect_merge_info_callback(int n,
 		struct tree_desc t[3];
 		void *buf[3] = {NULL, NULL, NULL};
 		const char *original_dir_name;
-		int i, ret;
+		int i, ret, side;
 
+		/*
+		 * Check for whether we can avoid recursing due to one side
+		 * matching the merge base.  The side that does NOT match is
+		 * the one that might have a rename destination we need.
+		 */
+		assert(!side1_matches_mbase || !side2_matches_mbase);
+		side = side1_matches_mbase ? MERGE_SIDE2 :
+			side2_matches_mbase ? MERGE_SIDE1 : MERGE_BASE;
+		if (filemask == 0 && (dirmask == 2 || dirmask == 4)) {
+			/*
+			 * Also defer recursing into new directories; set up a
+			 * few variables to let us do so.
+			 */
+			ci->match_mask = (7 - dirmask);
+			side = dirmask / 2;
+		}
+		if (renames->dir_rename_mask != 0x07 &&
+		    (side != MERGE_BASE) &&
+		    renames->trivial_merges_okay[side] &&
+		    !strset_contains(&renames->target_dirs[side], pi.string)) {
+			strintmap_set(&renames->possible_trivial_merges[side],
+				      pi.string, renames->dir_rename_mask);
+			renames->dir_rename_mask = prev_dir_rename_mask;
+			return mask;
+		}
+
+		/* We need to recurse */
 		ci->match_mask &= filemask;
 		newinfo = *info;
 		newinfo.prev = info;
@@ -1196,7 +1223,6 @@ static int collect_merge_info_callback(int n,
 	return mask;
 }
 
-MAYBE_UNUSED
 static int handle_deferred_entries(struct merge_options *opt,
 				   struct traverse_info *info)
 {
@@ -1285,6 +1311,8 @@ static int collect_merge_info(struct merge_options *opt,
 
 	trace2_region_enter("merge", "traverse_trees", opt->repo);
 	ret = traverse_trees(NULL, 3, t, &info);
+	if (ret == 0)
+		ret = handle_deferred_entries(opt, &info);
 	trace2_region_leave("merge", "traverse_trees", opt->repo);
 
 	return ret;
-- 
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