t6429: testcases for remembering renames

We will soon be adding an optimization that caches (in memory only,
never written to disk) upstream renames during a sequence of merges such
as occurs during a cherry-pick or rebase operation.  Add several tests
meant to stress such an implementation to ensure it does the right
thing, and include a test whose outcome we will later change due to this
optimization as well.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 692 insertions, 0 deletions

diff --git a/t/t6429-merge-sequence-rename-caching.sh b/t/t6429-merge-sequence-rename-caching.sh
new file mode 100755
index 0000000..f47d892
--- /dev/null
+++ b/t/t6429-merge-sequence-rename-caching.sh
@@ -0,0 +1,692 @@
+#!/bin/sh
+
+test_description="remember regular & dir renames in sequence of merges"
+
+. ./test-lib.sh
+
+#
+# NOTE 1: this testfile tends to not only rename files, but modify on both
+#         sides; without modifying on both sides, optimizations can kick in
+#         which make rename detection irrelevant or trivial.  We want to make
+#         sure that we are triggering rename caching rather than rename
+#         bypassing.
+#
+# NOTE 2: this testfile uses 'test-tool fast-rebase' instead of either
+#         cherry-pick or rebase.  sequencer.c is only superficially
+#         integrated with merge-ort; it calls merge_switch_to_result()
+#         after EACH merge, which updates the index and working copy AND
+#         throws away the cached results (because merge_switch_to_result()
+#         is only supposed to be called at the end of the sequence).
+#         Integrating them more deeply is a big task, so for now the tests
+#         use 'test-tool fast-rebase'.
+#
+
+
+#
+# In the following simple testcase:
+#   Base:     numbers_1, values_1
+#   Upstream: numbers_2, values_2
+#   Topic_1:  sequence_3
+#   Topic_2:  scruples_3
+# or, in english, rename numbers -> sequence in the first commit, and rename
+# values -> scruples in the second commit.
+#
+# This shouldn't be a challenge, it's just verifying that cached renames isn't
+# preventing us from finding new renames.
+#
+test_expect_success 'caching renames does not preclude finding new ones' '
+	test_create_repo caching-renames-and-new-renames &&
+	(
+		cd caching-renames-and-new-renames &&
+
+		test_seq 2 10 >numbers &&
+		test_seq 2 10 >values &&
+		git add numbers values &&
+		git commit -m orig &&
+
+		git branch upstream &&
+		git branch topic &&
+
+		git switch upstream &&
+		test_seq 1 10 >numbers &&
+		test_seq 1 10 >values &&
+		git add numbers values &&
+		git commit -m "Tweaked both files" &&
+
+		git switch topic &&
+
+		test_seq 2 12 >numbers &&
+		git add numbers &&
+		git mv numbers sequence &&
+		git commit -m A &&
+
+		test_seq 2 12 >values &&
+		git add values &&
+		git mv values scruples &&
+		git commit -m B &&
+
+		#
+		# Actual testing
+		#
+
+		git switch upstream &&
+
+		test-tool fast-rebase --onto HEAD upstream~1 topic &&
+		#git cherry-pick upstream~1..topic
+
+		git ls-files >tracked-files &&
+		test_line_count = 2 tracked-files &&
+		test_seq 1 12 >expect &&
+		test_cmp expect sequence &&
+		test_cmp expect scruples
+	)
+'
+
+#
+# In the following testcase:
+#   Base:     numbers_1
+#   Upstream: rename numbers_1 -> sequence_2
+#   Topic_1:  numbers_3
+#   Topic_2:  numbers_1
+# or, in english, the first commit on the topic branch modifies numbers by
+# shrinking it (dramatically) and the second commit on topic reverts its
+# parent.
+#
+# Can git apply both patches?
+#
+# Traditional cherry-pick/rebase will fail to apply the second commit, the
+# one that reverted its parent, because despite detecting the rename from
+# 'numbers' to 'sequence' for the first commit, it fails to detect that
+# rename when picking the second commit.  That's "reasonable" given the
+# dramatic change in size of the file, but remembering the rename and
+# reusing it is reasonable too.
+#
+# Rename detection (diffcore_rename_extended()) will run twice here; it is
+# not needed on the topic side of history for either of the two commits
+# being merged, but it is needed on the upstream side of history for each
+# commit being picked.
+test_expect_success 'cherry-pick both a commit and its immediate revert' '
+	test_create_repo pick-commit-and-its-immediate-revert &&
+	(
+		cd pick-commit-and-its-immediate-revert &&
+
+		test_seq 11 30 >numbers &&
+		git add numbers &&
+		git commit -m orig &&
+
+		git branch upstream &&
+		git branch topic &&
+
+		git switch upstream &&
+		test_seq 1 30 >numbers &&
+		git add numbers &&
+		git mv numbers sequence &&
+		git commit -m "Renamed (and modified) numbers -> sequence" &&
+
+		git switch topic &&
+
+		test_seq 11 13 >numbers &&
+		git add numbers &&
+		git commit -m A &&
+
+		git revert HEAD &&
+
+		#
+		# Actual testing
+		#
+
+		git switch upstream &&
+
+		GIT_TRACE2_PERF="$(pwd)/trace.output" &&
+		export GIT_TRACE2_PERF &&
+
+		test_might_fail test-tool fast-rebase --onto HEAD upstream~1 topic &&
+		#git cherry-pick upstream~1..topic &&
+
+		grep region_enter.*diffcore_rename trace.output >calls &&
+		test_line_count = 2 calls
+	)
+'
+
+#
+# In the following testcase:
+#   Base:     sequence_1
+#   Upstream: rename sequence_1 -> values_2
+#   Topic_1:  rename sequence_1 -> values_3
+#   Topic_2:  add unrelated sequence_4
+# or, in english, both sides rename sequence -> values, and then the second
+# commit on the topic branch adds an unrelated file called sequence.
+#
+# This testcase presents no problems for git traditionally, but having both
+# sides do the same rename in effect "uses it up" and if it remains cached,
+# could cause a spurious rename/add conflict.
+#
+test_expect_success 'rename same file identically, then reintroduce it' '
+	test_create_repo rename-rename-1to1-then-add-old-filename &&
+	(
+		cd rename-rename-1to1-then-add-old-filename &&
+
+		test_seq 3 8 >sequence &&
+		git add sequence &&
+		git commit -m orig &&
+
+		git branch upstream &&
+		git branch topic &&
+
+		git switch upstream &&
+		test_seq 1 8 >sequence &&
+		git add sequence &&
+		git mv sequence values &&
+		git commit -m "Renamed (and modified) sequence -> values" &&
+
+		git switch topic &&
+
+		test_seq 3 10 >sequence &&
+		git add sequence &&
+		git mv sequence values &&
+		git commit -m A &&
+
+		test_write_lines A B C D E F G H I J >sequence &&
+		git add sequence &&
+		git commit -m B &&
+
+		#
+		# Actual testing
+		#
+
+		git switch upstream &&
+
+		GIT_TRACE2_PERF="$(pwd)/trace.output" &&
+		export GIT_TRACE2_PERF &&
+
+		test-tool fast-rebase --onto HEAD upstream~1 topic &&
+		#git cherry-pick upstream~1..topic &&
+
+		git ls-files >tracked &&
+		test_line_count = 2 tracked &&
+		test_path_is_file values &&
+		test_path_is_file sequence &&
+
+		grep region_enter.*diffcore_rename trace.output >calls &&
+		test_line_count = 2 calls
+	)
+'
+
+#
+# In the following testcase:
+#   Base:     olddir/{valuesZ_1, valuesY_1, valuesX_1}
+#   Upstream: rename olddir/valuesZ_1 -> dirA/valuesZ_2
+#             rename olddir/valuesY_1 -> dirA/valuesY_2
+#             rename olddir/valuesX_1 -> dirB/valuesX_2
+#   Topic_1:  rename olddir/valuesZ_1 -> dirA/valuesZ_3
+#             rename olddir/valuesY_1 -> dirA/valuesY_3
+#   Topic_2:  add olddir/newfile
+#   Expected Pick1: dirA/{valuesZ, valuesY}, dirB/valuesX
+#   Expected Pick2: dirA/{valuesZ, valuesY}, dirB/{valuesX, newfile}
+#
+# This testcase presents no problems for git traditionally, but having both
+# sides do the same renames in effect "use it up" but if the renames remain
+# cached, the directory rename could put newfile in the wrong directory.
+#
+test_expect_success 'rename same file identically, then add file to old dir' '
+	test_create_repo rename-rename-1to1-then-add-file-to-old-dir &&
+	(
+		cd rename-rename-1to1-then-add-file-to-old-dir &&
+
+		mkdir olddir/ &&
+		test_seq 3 8 >olddir/valuesZ &&
+		test_seq 3 8 >olddir/valuesY &&
+		test_seq 3 8 >olddir/valuesX &&
+		git add olddir &&
+		git commit -m orig &&
+
+		git branch upstream &&
+		git branch topic &&
+
+		git switch upstream &&
+		test_seq 1 8 >olddir/valuesZ &&
+		test_seq 1 8 >olddir/valuesY &&
+		test_seq 1 8 >olddir/valuesX &&
+		git add olddir &&
+		mkdir dirA &&
+		git mv olddir/valuesZ olddir/valuesY dirA &&
+		git mv olddir/ dirB/ &&
+		git commit -m "Renamed (and modified) values*" &&
+
+		git switch topic &&
+
+		test_seq 3 10 >olddir/valuesZ &&
+		test_seq 3 10 >olddir/valuesY &&
+		git add olddir &&
+		mkdir dirA &&
+		git mv olddir/valuesZ olddir/valuesY dirA &&
+		git commit -m A &&
+
+		>olddir/newfile &&
+		git add olddir/newfile &&
+		git commit -m B &&
+
+		#
+		# Actual testing
+		#
+
+		git switch upstream &&
+		git config merge.directoryRenames true &&
+
+		GIT_TRACE2_PERF="$(pwd)/trace.output" &&
+		export GIT_TRACE2_PERF &&
+
+		test-tool fast-rebase --onto HEAD upstream~1 topic &&
+		#git cherry-pick upstream~1..topic &&
+
+		git ls-files >tracked &&
+		test_line_count = 4 tracked &&
+		test_path_is_file dirA/valuesZ &&
+		test_path_is_file dirA/valuesY &&
+		test_path_is_file dirB/valuesX &&
+		test_path_is_file dirB/newfile &&
+
+		grep region_enter.*diffcore_rename trace.output >calls &&
+		test_line_count = 3 calls
+	)
+'
+
+#
+# In the following testcase, upstream renames a directory, and the topic branch
+# first adds a file to the directory, then later renames the directory
+# differently:
+#   Base:     olddir/a
+#             olddir/b
+#   Upstream: rename olddir/ -> newdir/
+#   Topic_1:  add olddir/newfile
+#   Topic_2:  rename olddir/ -> otherdir/
+#
+# Here we are just concerned that cached renames might prevent us from seeing
+# the rename conflict, and we want to ensure that we do get a conflict.
+#
+# While at it, also test that we do rename detection three times.  We have to
+# detect renames on the upstream side of history once for each merge, plus
+# Topic_2 has renames.
+#
+test_expect_success 'cached dir rename does not prevent noticing later conflict' '
+	test_create_repo dir-rename-cache-not-occluding-later-conflict &&
+	(
+		cd dir-rename-cache-not-occluding-later-conflict &&
+
+		mkdir olddir &&
+		test_seq 3 10 >olddir/a &&
+		test_seq 3 10 >olddir/b &&
+		git add olddir &&
+		git commit -m orig &&
+
+		git branch upstream &&
+		git branch topic &&
+
+		git switch upstream &&
+		test_seq 3 10 >olddir/a &&
+		test_seq 3 10 >olddir/b &&
+		git add olddir &&
+		git mv olddir newdir &&
+		git commit -m "Dir renamed" &&
+
+		git switch topic &&
+
+		>olddir/newfile &&
+		git add olddir/newfile &&
+		git commit -m A &&
+
+		test_seq 1 8 >olddir/a &&
+		test_seq 1 8 >olddir/b &&
+		git add olddir &&
+		git mv olddir otherdir &&
+		git commit -m B &&
+
+		#
+		# Actual testing
+		#
+
+		git switch upstream &&
+		git config merge.directoryRenames true &&
+
+		GIT_TRACE2_PERF="$(pwd)/trace.output" &&
+		export GIT_TRACE2_PERF &&
+
+		test_must_fail test-tool fast-rebase --onto HEAD upstream~1 topic >output &&
+		#git cherry-pick upstream..topic &&
+
+		grep CONFLICT..rename/rename output &&
+
+		grep region_enter.*diffcore_rename trace.output >calls &&
+		test_line_count = 3 calls
+	)
+'
+
+# Helper for the next two tests
+test_setup_upstream_rename () {
+	test_create_repo $1 &&
+	(
+		cd $1 &&
+
+		test_seq 3 8 >somefile &&
+		test_seq 3 8 >relevant-rename &&
+		git add somefile relevant-rename &&
+		mkdir olddir &&
+		test_write_lines a b c d e f g >olddir/a &&
+		test_write_lines z y x w v u t >olddir/b &&
+		git add olddir &&
+		git commit -m orig &&
+
+		git branch upstream &&
+		git branch topic &&
+
+		git switch upstream &&
+		test_seq 1 8 >somefile &&
+		test_seq 1 8 >relevant-rename &&
+		git add somefile relevant-rename &&
+		git mv relevant-rename renamed &&
+		echo h >>olddir/a &&
+		echo s >>olddir/b &&
+		git add olddir &&
+		git mv olddir newdir &&
+		git commit -m "Dir renamed"
+	)
+}
+
+#
+# In the following testcase, upstream renames a file in the toplevel directory
+# as well as its only directory:
+#   Base:     relevant-rename_1
+#             somefile
+#             olddir/a
+#             olddir/b
+#   Upstream: rename relevant-rename_1 -> renamed_2
+#             rename olddir/           -> newdir/
+#   Topic_1:  relevant-rename_3
+#   Topic_2:  olddir/newfile_1
+#   Topic_3:  olddir/newfile_2
+#
+# In this testcase, since the first commit being picked only modifies a
+# file in the toplevel directory, the directory rename is irrelevant for
+# that first merge.  However, we need to notice the directory rename for
+# the merge that picks the second commit, and we don't want the third
+# commit to mess up its location either.  We want to make sure that
+# olddir/newfile doesn't exist in the result and that newdir/newfile does.
+#
+# We also expect rename detection to occur three times.  Although it is
+# typically needed two times per commit, there are no deleted files on the
+# topic side of history, so we only need to detect renames on the upstream
+# side for each of the 3 commits we need to pick.
+#
+test_expect_success 'dir rename unneeded, then add new file to old dir' '
+	test_setup_upstream_rename dir-rename-unneeded-until-new-file &&
+	(
+		cd dir-rename-unneeded-until-new-file &&
+
+		git switch topic &&
+
+		test_seq 3 10 >relevant-rename &&
+		git add relevant-rename &&
+		git commit -m A &&
+
+		echo foo >olddir/newfile &&
+		git add olddir/newfile &&
+		git commit -m B &&
+
+		echo bar >>olddir/newfile &&
+		git add olddir/newfile &&
+		git commit -m C &&
+
+		#
+		# Actual testing
+		#
+
+		git switch upstream &&
+		git config merge.directoryRenames true &&
+
+		GIT_TRACE2_PERF="$(pwd)/trace.output" &&
+		export GIT_TRACE2_PERF &&
+
+		test-tool fast-rebase --onto HEAD upstream~1 topic &&
+		#git cherry-pick upstream..topic &&
+
+		grep region_enter.*diffcore_rename trace.output >calls &&
+		test_line_count = 3 calls &&
+
+		git ls-files >tracked &&
+		test_line_count = 5 tracked &&
+		test_path_is_missing olddir/newfile &&
+		test_path_is_file newdir/newfile
+	)
+'
+
+#
+# The following testcase is *very* similar to the last one, but instead of
+# adding a new olddir/newfile, it renames somefile -> olddir/newfile:
+#   Base:     relevant-rename_1
+#             somefile_1
+#             olddir/a
+#             olddir/b
+#   Upstream: rename relevant-rename_1 -> renamed_2
+#             rename olddir/           -> newdir/
+#   Topic_1:  relevant-rename_3
+#   Topic_2:  rename somefile -> olddir/newfile_2
+#   Topic_3:  modify olddir/newfile_3
+#
+# In this testcase, since the first commit being picked only modifies a
+# file in the toplevel directory, the directory rename is irrelevant for
+# that first merge.  However, we need to notice the directory rename for
+# the merge that picks the second commit, and we don't want the third
+# commit to mess up its location either.  We want to make sure that
+# neither somefile or olddir/newfile exists in the result and that
+# newdir/newfile does.
+#
+# This testcase needs one more call to rename detection than the last
+# testcase, because of the somefile -> olddir/newfile rename in Topic_2.
+test_expect_success 'dir rename unneeded, then rename existing file into old dir' '
+	test_setup_upstream_rename dir-rename-unneeded-until-file-moved-inside &&
+	(
+		cd dir-rename-unneeded-until-file-moved-inside &&
+
+		git switch topic &&
+
+		test_seq 3 10 >relevant-rename &&
+		git add relevant-rename &&
+		git commit -m A &&
+
+		test_seq 1 10 >somefile &&
+		git add somefile &&
+		git mv somefile olddir/newfile &&
+		git commit -m B &&
+
+		test_seq 1 12 >olddir/newfile &&
+		git add olddir/newfile &&
+		git commit -m C &&
+
+		#
+		# Actual testing
+		#
+
+		git switch upstream &&
+		git config merge.directoryRenames true &&
+
+		GIT_TRACE2_PERF="$(pwd)/trace.output" &&
+		export GIT_TRACE2_PERF &&
+
+		test-tool fast-rebase --onto HEAD upstream~1 topic &&
+		#git cherry-pick upstream..topic &&
+
+		grep region_enter.*diffcore_rename trace.output >calls &&
+		test_line_count = 4 calls &&
+
+		test_path_is_missing somefile &&
+		test_path_is_missing olddir/newfile &&
+		test_path_is_file newdir/newfile &&
+		git ls-files >tracked &&
+		test_line_count = 4 tracked
+	)
+'
+
+# Helper for the next two tests
+test_setup_topic_rename () {
+	test_create_repo $1 &&
+	(
+		cd $1 &&
+
+		test_seq 3 8 >somefile &&
+		mkdir olddir &&
+		test_seq 3 8 >olddir/a &&
+		echo b >olddir/b &&
+		git add olddir somefile &&
+		git commit -m orig &&
+
+		git branch upstream &&
+		git branch topic &&
+
+		git switch topic &&
+		test_seq 1 8 >somefile &&
+		test_seq 1 8 >olddir/a &&
+		git add somefile olddir/a &&
+		git mv olddir newdir &&
+		git commit -m "Dir renamed" &&
+
+		test_seq 1 10 >somefile &&
+		git add somefile &&
+		mkdir olddir &&
+		>olddir/unrelated-file &&
+		git add olddir &&
+		git commit -m "Unrelated file in recreated old dir"
+	)
+}
+
+#
+# In the following testcase, the first commit on the topic branch renames
+# a directory, while the second recreates the old directory and places a
+# file into it:
+#   Base:     somefile
+#             olddir/a
+#             olddir/b
+#   Upstream: olddir/newfile
+#   Topic_1:  somefile_2
+#             rename olddir/ -> newdir/
+#   Topic_2:  olddir/unrelated-file
+#
+# Note that the first pick should merge:
+#   Base:     somefile
+#             olddir/{a,b}
+#   Upstream: olddir/newfile
+#   Topic_1:  rename olddir/ -> newdir/
+# For which the expected result (assuming merge.directoryRenames=true) is
+# clearly:
+#   Result:   somefile
+#             newdir/{a, b, newfile}
+#
+# While the second pick does the following three-way merge:
+#   Base (Topic_1):           somefile
+#                             newdir/{a,b}
+#   Upstream (Result from 1): same files as base, but adds newdir/newfile
+#   Topic_2:                  same files as base, but adds olddir/unrelated-file
+#
+# The second merge is pretty trivial; upstream adds newdir/newfile, and
+# topic_2 adds olddir/unrelated-file.  We're just testing that we don't
+# accidentally cache directory renames somehow and rename
+# olddir/unrelated-file to newdir/unrelated-file.
+#
+# This testcase should only need one call to diffcore_rename_extended().
+test_expect_success 'caching renames only on upstream side, part 1' '
+	test_setup_topic_rename cache-renames-only-upstream-add-file &&
+	(
+		cd cache-renames-only-upstream-add-file &&
+
+		git switch upstream &&
+
+		>olddir/newfile &&
+		git add olddir/newfile &&
+		git commit -m "Add newfile" &&
+
+		#
+		# Actual testing
+		#
+
+		git switch upstream &&
+
+		git config merge.directoryRenames true &&
+
+		GIT_TRACE2_PERF="$(pwd)/trace.output" &&
+		export GIT_TRACE2_PERF &&
+
+		test-tool fast-rebase --onto HEAD upstream~1 topic &&
+		#git cherry-pick upstream..topic &&
+
+		grep region_enter.*diffcore_rename trace.output >calls &&
+		test_line_count = 1 calls &&
+
+		git ls-files >tracked &&
+		test_line_count = 5 tracked &&
+		test_path_is_missing newdir/unrelated-file &&
+		test_path_is_file olddir/unrelated-file &&
+		test_path_is_file newdir/newfile &&
+		test_path_is_file newdir/b &&
+		test_path_is_file newdir/a &&
+		test_path_is_file somefile
+	)
+'
+
+#
+# The following testcase is *very* similar to the last one, but instead of
+# adding a new olddir/newfile, it renames somefile -> olddir/newfile:
+#   Base:     somefile
+#             olddir/a
+#             olddir/b
+#   Upstream: somefile_1 -> olddir/newfile
+#   Topic_1:  rename olddir/ -> newdir/
+#             somefile_2
+#   Topic_2:  olddir/unrelated-file
+#             somefile_3
+#
+# Much like the previous test, this case is actually trivial and we are just
+# making sure there isn't some spurious directory rename caching going on
+# for the wrong side of history.
+#
+#
+# This testcase should only need three calls to diffcore_rename_extended(),
+# because there are no renames on the topic side of history for picking
+# Topic_2.
+#
+test_expect_success 'caching renames only on upstream side, part 2' '
+	test_setup_topic_rename cache-renames-only-upstream-rename-file &&
+	(
+		cd cache-renames-only-upstream-rename-file &&
+
+		git switch upstream &&
+
+		git mv somefile olddir/newfile &&
+		git commit -m "Add newfile" &&
+
+		#
+		# Actual testing
+		#
+
+		git switch upstream &&
+
+		git config merge.directoryRenames true &&
+
+		GIT_TRACE2_PERF="$(pwd)/trace.output" &&
+		export GIT_TRACE2_PERF &&
+
+		test-tool fast-rebase --onto HEAD upstream~1 topic &&
+		#git cherry-pick upstream..topic &&
+
+		grep region_enter.*diffcore_rename trace.output >calls &&
+		test_line_count = 3 calls &&
+
+		git ls-files >tracked &&
+		test_line_count = 4 tracked &&
+		test_path_is_missing newdir/unrelated-file &&
+		test_path_is_file olddir/unrelated-file &&
+		test_path_is_file newdir/newfile &&
+		test_path_is_file newdir/b &&
+		test_path_is_file newdir/a
+	)
+'
+
+test_done