Merge branch 'en/ort-perf-batch-11'

Optimize out repeated rename detection in a sequence of mergy
operations.

* en/ort-perf-batch-11:
  merge-ort, diffcore-rename: employ cached renames when possible
  merge-ort: handle interactions of caching and rename/rename(1to1) cases
  merge-ort: add helper functions for using cached renames
  merge-ort: preserve cached renames for the appropriate side
  merge-ort: avoid accidental API mis-use
  merge-ort: add code to check for whether cached renames can be reused
  merge-ort: populate caches of rename detection results
  merge-ort: add data structures for in-memory caching of rename detection
  t6429: testcases for remembering renames
  fast-rebase: write conflict state to working tree, index, and HEAD
  fast-rebase: change assert() to BUG()
  Documentation/technical: describe remembering renames optimization
  t6423: rename file within directory that other side renamed

1 files changed, 58 insertions, 0 deletions

diff --git a/t/t6423-merge-rename-directories.sh b/t/t6423-merge-rename-directories.sh
index 7134769149..be84d22419 100755
--- a/t/t6423-merge-rename-directories.sh
+++ b/t/t6423-merge-rename-directories.sh
@@ -4966,6 +4966,64 @@ test_expect_success '12g: Testcase with two kinds of "relevant" renames' '
 	)
 '
 
+# Testcase 12h, Testcase with two kinds of "relevant" renames
+#   Commit O: olddir/{a_1, b}
+#   Commit A: newdir/{a_2, b}
+#   Commit B: olddir/{alpha_1, b}
+#   Expected: newdir/{alpha_2, b}
+
+test_setup_12h () {
+	test_create_repo 12h &&
+	(
+		cd 12h &&
+
+		mkdir olddir &&
+		test_seq 3 8 >olddir/a &&
+		>olddir/b &&
+		git add olddir &&
+		git commit -m orig &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git switch A &&
+		test_seq 3 10 >olddir/a &&
+		git add olddir/a &&
+		git mv olddir newdir &&
+		git commit -m A &&
+
+		git switch B &&
+
+		git mv olddir/a olddir/alpha &&
+		git commit -m B
+	)
+}
+
+test_expect_failure '12h: renaming a file within a renamed directory' '
+	test_setup_12h &&
+	(
+		cd 12h &&
+
+		git checkout A^0 &&
+
+		test_might_fail git -c merge.directoryRenames=true merge -s recursive B^0 &&
+
+		git ls-files >tracked &&
+		test_line_count = 2 tracked &&
+
+		test_path_is_missing olddir/a &&
+		test_path_is_file newdir/alpha &&
+		test_path_is_file newdir/b &&
+
+		git rev-parse >actual \
+			HEAD:newdir/alpha  HEAD:newdir/b &&
+		git rev-parse >expect \
+			A:newdir/a         O:oldir/b &&
+		test_cmp expect actual
+	)
+'
+
 ###########################################################################
 # SECTION 13: Checking informational and conflict messages
 #