[PATCH 3/3] merge-ort: fix issue with dual rename and add/add conflict

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

From: Elijah Newren <newren@gmail.com>

There is code in both merge-recursive and merge-ort for avoiding doubly
transitive renames (i.e. one side renames directory A/ -> B/, and the
other side renames directory B/ -> C/), because this combination would
otherwise make a mess for new files added to A/ on the first side and
wondering which directory they end up in -- especially if there were
even more renames such as the first side renaming C/ -> D/.  In such
cases, it just turns "off" directory rename detection for the higher
order transitive cases.

The testcases added in t6423 a couple commits ago are slightly different
but similar in principle.  They involve a similar case of paired
renaming but instead of A/ -> B/ and B/ -> C/, the second side renames
a leading directory of B/ to C/.  And both sides add a new file
somewhere under the directory that the other side will rename.  While
the new files added start within different directories and thus could
logically end up within different directories, it is weird for a file
on one side to end up where the other one started and not move along
with it.  So, let's just turn off directory rename detection in this
case as well.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 merge-ort.c                         | 4 ++++
 t/t6423-merge-rename-directories.sh | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/merge-ort.c b/merge-ort.c
index fa6667de18c..5bcb9a4980b 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -2292,9 +2292,13 @@ static char *check_for_directory_rename(struct merge_options *opt,
 	struct strmap_entry *rename_info;
 	struct strmap_entry *otherinfo = NULL;
 	const char *new_dir;
+	int other_side = 3 - side_index;
 
+	/* Cases where there is no new path, so we return NULL */
 	if (strmap_empty(dir_renames))
 		return new_path;
+	if (strmap_get(&collisions[other_side], path))
+		return new_path;
 	rename_info = check_dir_renamed(path, dir_renames);
 	if (!rename_info)
 		return new_path;
diff --git a/t/t6423-merge-rename-directories.sh b/t/t6423-merge-rename-directories.sh
index 296c04f8046..4286ae987c4 100755
--- a/t/t6423-merge-rename-directories.sh
+++ b/t/t6423-merge-rename-directories.sh
@@ -5245,7 +5245,7 @@ test_setup_12l () {
 	)
 }
 
-test_expect_merge_algorithm failure failure '12l (B into A): Rename into each other + add/add conflict' '
+test_expect_merge_algorithm failure success '12l (B into A): Rename into each other + add/add conflict' '
 	test_setup_12l BintoA &&
 	(
 		cd 12l_BintoA &&
@@ -5273,7 +5273,7 @@ test_expect_merge_algorithm failure failure '12l (B into A): Rename into each ot
 	)
 '
 
-test_expect_merge_algorithm failure failure '12l (A into B): Rename into each other + add/add conflict' '
+test_expect_merge_algorithm failure success '12l (A into B): Rename into each other + add/add conflict' '
 	test_setup_12l AintoB &&
 	(
 		cd 12l_AintoB &&
-- 
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