Subject: [PATCH 11/30] directory rename detection: testcases exploring possibly suboptimal merges

From: Elijah Newren <[email-masked]>
Date: Fri, 10 Nov 2017 11:05:31 -0800

Signed-off-by: Elijah Newren <[email-masked]>
---
 t/t6043-merge-rename-directories.sh | 371 ++++++++++++++++++++++++++++++++++++
 1 file changed, 371 insertions(+)

diff --git a/t/t6043-merge-rename-directories.sh b/t/t6043-merge-rename-directories.sh
index 115d0d2622..bdfd943c88 100755
--- a/t/t6043-merge-rename-directories.sh
+++ b/t/t6043-merge-rename-directories.sh
@@ -1683,4 +1683,375 @@ test_expect_failure '7e-check: transitive rename in rename/delete AND dirs in th
 	test $(git hash-object y/d~C^0) = $(git rev-parse A:x/d)
 '
 
+
+###########################################################################
+# SECTION 8: Suboptimal merges
+#
+# As alluded to in the last section, the ruleset we have built up for
+# detecting directory renames unfortunately has some special cases where it
+# results in slightly suboptimal or non-intuitive behavior.  This section
+# explores these cases.
+#
+# To be fair, we already had non-intuitive or suboptimal behavior for most
+# of these cases in git before introducing implicit directory rename
+# detection, but it'd be nice if there was a modified ruleset out there
+# that handled these cases a bit better.
+###########################################################################
+
+# Testcase 8a, Dual-directory rename, one into the others' way
+#   Commit A. x/{a,b},   y/{c,d}
+#   Commit B. x/{a,b,e}, y/{c,d,f}
+#   Commit C. y/{a,b},   z/{c,d}
+#
+# Possible Resolutions:
+#   Previous git: y/{a,b,f},   z/{c,d},   x/e
+#   Expected:     y/{a,b,e,f}, z/{c,d}
+#   Preferred:    y/{a,b,e},   z/{c,d,f}
+#
+# Note: Both x and y got renamed and it'd be nice to detect both, and we do
+# better with directory rename detection than git did previously, but the
+# simple rule from section 5 prevents me from handling this as optimally as
+# we potentially could.
+
+test_expect_success '8a-setup: Dual-directory rename, one into the others way' '
+	git rm -rf . &&
+	git clean -fdqx &&
+	rm -rf .git &&
+	git init &&
+
+	mkdir x &&
+	mkdir y &&
+	echo a >x/a &&
+	echo b >x/b &&
+	echo c >y/c &&
+	echo d >y/d &&
+	git add x y &&
+	test_tick &&
+	git commit -m "A" &&
+
+	git branch A &&
+	git branch B &&
+	git branch C &&
+
+	git checkout B &&
+	echo e >x/e &&
+	echo f >y/f &&
+	git add x/e y/f &&
+	test_tick &&
+	git commit -m "B" &&
+
+	git checkout C &&
+	git mv y z &&
+	git mv x y &&
+	test_tick &&
+	git commit -m "C"
+'
+
+test_expect_failure '8a-check: Dual-directory rename, one into the others way' '
+	git checkout B^0 &&
+
+	git merge -s recursive C^0 &&
+
+	test 6 -eq $(git ls-files -s | wc -l) &&
+	test 0 -eq $(git ls-files -u | wc -l) &&
+	test 0 -eq $(git ls-files -o | wc -l) &&
+
+	test $(git rev-parse HEAD:y/a) = $(git rev-parse A:x/a) &&
+	test $(git rev-parse HEAD:y/b) = $(git rev-parse A:x/b) &&
+	test $(git rev-parse HEAD:y/e) = $(git rev-parse B:x/e) &&
+	test $(git rev-parse HEAD:y/f) = $(git rev-parse B:y/f) &&
+	test $(git rev-parse HEAD:z/c) = $(git rev-parse A:y/c) &&
+	test $(git rev-parse HEAD:z/d) = $(git rev-parse A:y/d)
+'
+
+# Testcase 8b, Dual-directory rename, one into the others' way, with conflicting filenames
+#   Commit A. x/{a_1,b_1},     y/{a_2,b_2}
+#   Commit B. x/{a_1,b_1,e_1}, y/{a_2,b_2,e_2}
+#   Commit C. y/{a_1,b_1},     z/{a_2,b_2}
+#
+# Possible Resolutions:
+#   Previous git: y/{a_1,b_1,e_2}, z/{a_2,b_2}, x/e_1
+#   Scary:        y/{a_1,b_1},     z/{a_2,b_2}, CONFLICT(add/add, e_1 vs. e_2)
+#   Preferred:    y/{a_1,b_1,e_1}, z/{a_2,b_2,e_2}
+#
+# Note: Very similar to 8a, except instead of 'e' and 'f' in directories x and
+# y, both are named 'e'.  Without directory rename detection, neither file
+# moves directories.  Implment directory rename detection suboptimally, and
+# you get an add/add conflict, but both files were added in commit B, so this
+# is an add/add conflict where one side of history added both files --
+# something we can't represent in the index.  Obviously, we'd prefer the last
+# resolution, but our previous rules are too coarse to allow it.  Using both
+# the rules from section 4 and section 5 save us from the Scary resolution,
+# making us fall back to pre-directory-rename-detection behavior for both
+# e_1 and e_2.
+
+test_expect_success '8b-setup: Dual-directory rename, one into the others way, with conflicting filenames' '
+	git rm -rf . &&
+	git clean -fdqx &&
+	rm -rf .git &&
+	git init &&
+
+	mkdir x &&
+	mkdir y &&
+	echo a1 >x/a &&
+	echo b1 >x/b &&
+	echo a2 >y/a &&
+	echo b2 >y/b &&
+	git add x y &&
+	test_tick &&
+	git commit -m "A" &&
+
+	git branch A &&
+	git branch B &&
+	git branch C &&
+
+	git checkout B &&
+	echo e1 >x/e &&
+	echo e2 >y/e &&
+	git add x/e y/e &&
+	test_tick &&
+	git commit -m "B" &&
+
+	git checkout C &&
+	git mv y z &&
+	git mv x y &&
+	test_tick &&
+	git commit -m "C"
+'
+
+test_expect_success '8b-check: Dual-directory rename, one into the others way, with conflicting filenames' '
+	git checkout B^0 &&
+
+	git merge -s recursive C^0 &&
+
+	test 6 -eq $(git ls-files -s | wc -l) &&
+	test 0 -eq $(git ls-files -u | wc -l) &&
+	test 0 -eq $(git ls-files -o | wc -l) &&
+
+	test $(git rev-parse HEAD:y/a) = $(git rev-parse A:x/a) &&
+	test $(git rev-parse HEAD:y/b) = $(git rev-parse A:x/b) &&
+	test $(git rev-parse HEAD:z/a) = $(git rev-parse A:y/a) &&
+	test $(git rev-parse HEAD:z/b) = $(git rev-parse A:y/b) &&
+	test $(git rev-parse HEAD:x/e) = $(git rev-parse B:x/e) &&
+	test $(git rev-parse HEAD:y/e) = $(git rev-parse B:y/e)
+'
+
+# Testcase 8c, rename+modify/delete
+#   (Related to testcases 5b and 8d)
+#   Commit A: z/{b,c,d}
+#   Commit B: y/{b,c}
+#   Commit C: z/{b,c,d_modified,e}
+#   Expected: y/{b,c,e}, CONFLICT(rename+modify/delete: x/d -> y/d or deleted)
+#
+#   Note: This testcase doesn't present any concerns for me...until you
+#         compare it with testcases 5b and 8d.  See notes in 8d for more
+#         details.
+
+test_expect_success '8c-setup: rename+modify/delete' '
+	git rm -rf . &&
+	git clean -fdqx &&
+	rm -rf .git &&
+	git init &&
+
+	mkdir z &&
+	echo b >z/b &&
+	echo c >z/c &&
+	test_seq 1 10 >z/d &&
+	git add z &&
+	test_tick &&
+	git commit -m "A" &&
+
+	git branch A &&
+	git branch B &&
+	git branch C &&
+
+	git checkout B &&
+	git rm z/d &&
+	git mv z y &&
+	test_tick &&
+	git commit -m "B" &&
+
+	git checkout C &&
+	echo 11 >z/d &&
+	test_chmod +x z/d &&
+	echo e >z/e &&
+	git add z/d z/e &&
+	test_tick &&
+	git commit -m "C"
+'
+
+test_expect_failure '8c-check: rename+modify/delete' '
+	git checkout B^0 &&
+
+	test_must_fail git merge -s recursive C^0 >out &&
+	test_i18ngrep "CONFLICT (rename/delete).* z/d.*y/d" out &&
+
+	test 4 -eq $(git ls-files -s | wc -l) &&
+	test 1 -eq $(git ls-files -u | wc -l) &&
+	test 1 -eq $(git ls-files -o | wc -l) &&
+
+	test $(git rev-parse :0:y/b) = $(git rev-parse A:z/b) &&
+	test $(git rev-parse :0:y/c) = $(git rev-parse A:z/c) &&
+	test $(git rev-parse :0:y/e) = $(git rev-parse C:z/e) &&
+
+	test_must_fail git rev-parse :1:y/d &&
+	test_must_fail git rev-parse :2:y/d &&
+	test $(git rev-parse :3:y/d) = $(git rev-parse C:z/d) &&
+	git ls-files -s y/d | grep ^100755 &&
+	test -f y/d
+'
+
+# Testcase 8d, rename/delete...or not?
+#   (Related to testcase 5b; these may appear slightly inconsistent to users;
+#    Also related to testcases 7d and 7e)
+#   Commit A: z/{b,c,d}
+#   Commit B: y/{b,c}
+#   Commit C: z/{b,c,d,e}
+#   Expected: y/{b,c,e}
+#
+#   Note: It would also be somewhat reasonable to resolve this as
+#             y/{b,c,e}, CONFLICT(rename/delete: x/d -> y/d or deleted)
+#   The logic being that the only difference between this testcase and 8c
+#   is that there is no modification to d.  That suggests that instead of a
+#   rename/modify vs. delete conflict, we should just have a rename/delete
+#   conflict, otherwise we are being inconsistent.
+#
+#   However...as far as consistency goes, we didn't report a conflict for
+#   path d_1 in testcase 5b due to a different file being in the way.  So,
+#   we seem to be forced to have cases where users can change things
+#   slightly and get what they may perceive as inconsistent results.  It
+#   would be nice to avoid that, but I'm not sure I see how.
+#
+#   In this case, I'm leaning towards: commit B was the one that deleted z/d
+#   and it did the rename of z to y, so the two "conflicts" (rename vs.
+#   delete) are both coming from commit B, which is non-sensical.  Conflicts
+#   during merging are supposed to be about opposite sides doing things
+#   differently.
+
+test_expect_success '8d-setup: rename/delete...or not?' '
+	git rm -rf . &&
+	git clean -fdqx &&
+	rm -rf .git &&
+	git init &&
+
+	mkdir z &&
+	echo b >z/b &&
+	echo c >z/c &&
+	test_seq 1 10 >z/d &&
+	git add z &&
+	test_tick &&
+	git commit -m "A" &&
+
+	git branch A &&
+	git branch B &&
+	git branch C &&
+
+	git checkout B &&
+	git rm z/d &&
+	git mv z y &&
+	test_tick &&
+	git commit -m "B" &&
+
+	git checkout C &&
+	echo e >z/e &&
+	git add z/e &&
+	test_tick &&
+	git commit -m "C"
+'
+
+test_expect_failure '8d-check: rename/delete...or not?' '
+	git checkout B^0 &&
+
+	git merge -s recursive C^0 &&
+
+	test 3 -eq $(git ls-files -s | wc -l) &&
+
+	test $(git rev-parse HEAD:y/b) = $(git rev-parse A:z/b) &&
+	test $(git rev-parse HEAD:y/c) = $(git rev-parse A:z/c) &&
+	test $(git rev-parse HEAD:y/e) = $(git rev-parse C:z/e)
+'
+
+# Testcase 8e, Both sides rename, one side adds to original directory
+#   Commit A: z/{b,c}
+#   Commit B: y/{b,c}
+#   Commit C: w/{b,c}, z/d
+#
+# Possible Resolutions:
+#   Previous git: z/d, CONFLICT(z/b -> y/b vs. w/b), CONFLICT(z/c -> y/c vs. w/c)
+#   Expected:     y/d, CONFLICT(z/b -> y/b vs. w/b), CONFLICT(z/c -> y/c vs. w/c)
+#   Preferred:    ??
+#
+# Notes: In commit B, directory z got renamed to y.  In commit C, directory z
+#        did NOT get renamed; the directory is still present; instead it is
+#        considered to have just renamed a subset of paths in directory z
+#        elsewhere.  Therefore, the directory rename done in commit B to z/
+#        applies to z/d and maps it to y/d.
+#
+#        It's possible that users would get confused about this, but what
+#        should we do instead?  Silently leaving at z/d seems just as bad or
+#        maybe even worse.  Perhaps we could print a big warning about z/d
+#        and how we're moving to y/d in this case, but when I started thinking
+#        abouty the ramifications of doing that, I didn't know how to rule out
+#        that opening other weird edge and corner cases so I just punted.
+
+test_expect_success '8e-setup: Both sides rename, one side adds to original directory' '
+	git rm -rf . &&
+	git clean -fdqx &&
+	rm -rf .git &&
+	git init &&
+
+	mkdir z &&
+	echo b >z/b &&
+	echo c >z/c &&
+	git add z &&
+	test_tick &&
+	git commit -m "A" &&
+
+	git branch A &&
+	git branch B &&
+	git branch C &&
+
+	git checkout B &&
+	git mv z y &&
+	test_tick &&
+	git commit -m "B" &&
+
+	git checkout C &&
+	git mv z w &&
+	mkdir z &&
+	echo d >z/d &&
+	git add z/d &&
+	test_tick &&
+	git commit -m "C"
+'
+
+test_expect_failure '8e-check: Both sides rename, one side adds to original directory' '
+	git checkout B^0 &&
+
+	test_must_fail git merge -s recursive C^0 >out 2>err &&
+
+	test 7 -eq $(git ls-files -s | wc -l) &&
+	test 6 -eq $(git ls-files -u | wc -l) &&
+	test 2 -eq $(git ls-files -o | wc -l) &&
+
+	test $(git rev-parse :0:y/d) = $(git rev-parse C:z/d) &&
+
+	test $(git rev-parse :1:z/b) = $(git rev-parse A:z/b) &&
+	test $(git rev-parse :2:y/b) = $(git rev-parse A:z/b) &&
+	test $(git rev-parse :3:w/b) = $(git rev-parse A:z/b) &&
+	test ! -f z/b &&
+	test $(git hash-object y/b) = $(git rev-parse A:z/b) &&
+	test $(git hash-object w/b) = $(git rev-parse A:z/b) &&
+
+	test $(git rev-parse :1:z/c) = $(git rev-parse A:z/c) &&
+	test $(git rev-parse :2:y/c) = $(git rev-parse A:z/c) &&
+	test $(git rev-parse :3:w/c) = $(git rev-parse A:z/c) &&
+	test ! -f z/c &&
+	test $(git hash-object y/c) = $(git rev-parse A:z/c) &&
+	test $(git hash-object w/c) = $(git rev-parse A:z/c) &&
+
+	test_i18ngrep CONFLICT.*rename/rename.*z/c.*y/c.*w/c out &&
+	test_i18ngrep CONFLICT.*rename/rename.*z/b.*y/b.*w/b out
+'
+
 test_done
-- 
2.15.0.5.g9567be9905