git-commit-vandalism/t/t4108-apply-threeway.sh
Jerry Zhang 923cd87ac8 git-apply: try threeway first when "--3way" is used
The apply_fragments() method of "git apply"
can silently apply patches incorrectly if
a file has repeating contents. In these
cases a three-way merge is capable of applying
it correctly in more situations, and will
show a conflict rather than applying it
incorrectly. However, because the patches
apply "successfully" using apply_fragments(),
git will never fall back to the merge, even
if the "--3way" flag is used, and the user has
no way to ensure correctness by forcing the
three-way merge method.

Change the behavior so that when "--3way" is used,
git will always try the three-way merge first and
will only fall back to apply_fragments() in cases
where blobs are not available or some other error
(but not in the case of a merge conflict).

Since user-facing results will be different,
this has backwards compatibility implications
for users depending on the old behavior. In
addition, the three-way merge will be slower
than direct patch application.

Signed-off-by: Jerry Zhang <jerry@skydio.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-04-06 17:11:41 -07:00

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#!/bin/sh
test_description='git apply --3way'
GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
. ./test-lib.sh
print_sanitized_conflicted_diff () {
git diff HEAD >diff.raw &&
sed -e '
/^index /d
s/^\(+[<>|][<>|][<>|][<>|]*\) .*/\1/
' diff.raw
}
test_expect_success setup '
test_tick &&
test_write_lines 1 2 3 4 5 6 7 >one &&
cat one >two &&
git add one two &&
git commit -m initial &&
git branch side &&
test_tick &&
test_write_lines 1 two 3 4 5 six 7 >one &&
test_write_lines 1 two 3 4 5 6 7 >two &&
git commit -a -m main &&
git checkout side &&
test_write_lines 1 2 3 4 five 6 7 >one &&
test_write_lines 1 2 3 4 five 6 7 >two &&
git commit -a -m side &&
git checkout main
'
test_expect_success 'apply without --3way' '
git diff side^ side >P.diff &&
# should fail to apply
git reset --hard &&
git checkout main^0 &&
test_must_fail git apply --index P.diff &&
# should leave things intact
git diff-files --exit-code &&
git diff-index --exit-code --cached HEAD
'
test_apply_with_3way () {
# Merging side should be similar to applying this patch
git diff ...side >P.diff &&
# The corresponding conflicted merge
git reset --hard &&
git checkout main^0 &&
test_must_fail git merge --no-commit side &&
git ls-files -s >expect.ls &&
print_sanitized_conflicted_diff >expect.diff &&
# should fail to apply
git reset --hard &&
git checkout main^0 &&
test_must_fail git apply --index --3way P.diff &&
git ls-files -s >actual.ls &&
print_sanitized_conflicted_diff >actual.diff &&
# The result should resemble the corresponding merge
test_cmp expect.ls actual.ls &&
test_cmp expect.diff actual.diff
}
test_expect_success 'apply with --3way' '
test_apply_with_3way
'
test_expect_success 'apply with --3way with merge.conflictStyle = diff3' '
test_config merge.conflictStyle diff3 &&
test_apply_with_3way
'
test_expect_success 'apply with --3way with rerere enabled' '
test_config rerere.enabled true &&
# Merging side should be similar to applying this patch
git diff ...side >P.diff &&
# The corresponding conflicted merge
git reset --hard &&
git checkout main^0 &&
test_must_fail git merge --no-commit side &&
# Manually resolve and record the resolution
test_write_lines 1 two 3 4 five six 7 >one &&
git rerere &&
cat one >expect &&
# should fail to apply
git reset --hard &&
git checkout main^0 &&
test_must_fail git apply --index --3way P.diff &&
# but rerere should have replayed the recorded resolution
test_cmp expect one
'
test_expect_success 'apply -3 with add/add conflict setup' '
git reset --hard &&
git checkout -b adder &&
test_write_lines 1 2 3 4 5 6 7 >three &&
test_write_lines 1 2 3 4 5 6 7 >four &&
git add three four &&
git commit -m "add three and four" &&
git checkout -b another adder^ &&
test_write_lines 1 2 3 4 5 6 7 >three &&
test_write_lines 1 2 3 four 5 6 7 >four &&
git add three four &&
git commit -m "add three and four" &&
# Merging another should be similar to applying this patch
git diff adder...another >P.diff &&
git checkout adder^0 &&
test_must_fail git merge --no-commit another &&
git ls-files -s >expect.ls &&
print_sanitized_conflicted_diff >expect.diff
'
test_expect_success 'apply -3 with add/add conflict' '
# should fail to apply ...
git reset --hard &&
git checkout adder^0 &&
test_must_fail git apply --index --3way P.diff &&
# ... and leave conflicts in the index and in the working tree
git ls-files -s >actual.ls &&
print_sanitized_conflicted_diff >actual.diff &&
# The result should resemble the corresponding merge
test_cmp expect.ls actual.ls &&
test_cmp expect.diff actual.diff
'
test_expect_success 'apply -3 with add/add conflict (dirty working tree)' '
# should fail to apply ...
git reset --hard &&
git checkout adder^0 &&
echo >>four &&
cat four >four.save &&
cat three >three.save &&
git ls-files -s >expect.ls &&
test_must_fail git apply --index --3way P.diff &&
# ... and should not touch anything
git ls-files -s >actual.ls &&
test_cmp expect.ls actual.ls &&
test_cmp four.save four &&
test_cmp three.save three
'
test_expect_success 'apply -3 with ambiguous repeating file' '
git reset --hard &&
test_write_lines 1 2 1 2 1 2 1 2 1 2 1 >one_two_repeat &&
git add one_two_repeat &&
git commit -m "init one" &&
test_write_lines 1 2 1 2 1 2 1 2 one 2 1 >one_two_repeat &&
git commit -a -m "change one" &&
git diff HEAD~ >Repeat.diff &&
git reset --hard HEAD~ &&
test_write_lines 1 2 1 2 1 2 one 2 1 2 one >one_two_repeat &&
git commit -a -m "change surrounding one" &&
git apply --index --3way Repeat.diff &&
test_write_lines 1 2 1 2 1 2 one 2 one 2 one >expect &&
test_cmp expect one_two_repeat
'
test_done