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[10/20] merge-ort: avoid recursing into identical trees

Message ID 20201030034131.1479968-11-newren@gmail.com (mailing list archive)
State New, archived
Headers show
Series fundamentals of merge-ort implementation | expand

Commit Message

Elijah Newren Oct. 30, 2020, 3:41 a.m. UTC
When all three trees have the same oid, there is no need to recurse into
these trees to find that all files within them happen to match.  We can
just record any one of the trees as the resolution of merging that
particular path.

Immediately resolving trees for other types of trivial tree merges (such
as one side matches the merge base, or the two sides match each other)
would prevent us from detecting renames for some paths, and thus prevent
us from doing three-way content merges for those paths whose renames we
did not detect.

Signed-off-by: Elijah Newren <newren@gmail.com>
 merge-ort.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
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diff --git a/merge-ort.c b/merge-ort.c
index 60e2b78e2d..2a402e18ed 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -202,6 +202,20 @@  static int collect_merge_info_callback(int n,
 	fullpath = xmalloc(len+1);
 	make_traverse_path(fullpath, len+1, info, p->path, p->pathlen);
+	/*
+	 * If mbase, side1, and side2 all match, we can resolve early.  Even
+	 * if these are trees, there will be no renames or anything
+	 * underneath.
+	 */
+	if (side1_matches_mbase && side2_matches_mbase) {
+		/* mbase, side1, & side2 all match; use mbase as resolution */
+		setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+				names, names+0, mbase_null, 0,
+				filemask, dirmask, 1);
+		strmap_put(&opti->paths, pi.string, pi.util);
+		return mask;
+	}
 	 * Record information about the path so we can resolve later in
 	 * process_entries.