[PATCH v2] apply: resolve trivial merge without hitting ll-merge with "--3way"
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Sep 5, 2021, 19:06 UTC
- Message-ID
- <20210905190657.2906699-1-gitster@pobox.com>
- In-Reply-To
- <xmqqczr26i9f.fsf@gitster.g>
The ll_binary_merge() function assumes that the ancestor blob is different from either side of the new versions, and always fails the merge in conflict, unless -Xours or -Xtheirs is in effect.
The normal "merge" machineries all resolve the trivial cases (e.g. if our side changed while their side did not, the result is ours) without triggering the file-level merge drivers, so the assumption is warranted.
The code path in "git apply --3way", however, does not check for the trivial three-way merge situation and always calls the file-level merge drivers. This used to be perfectly OK back when we always first attempted a straight patch application and used the three-way code path only as a fallback. Any binary patch that can be applied as a trivial three-way merge (e.g. the patch is based exactly on the version we happen to have) would always cleanly apply, so the ll_binary_merge() that is not prepared to see the trivial case would not have to handle such a case.
This no longer is true after we made "--3way" to mean "first try three-way and then fall back to straight application", and made "git apply -3" on a binary patch that is based on the current version no longer apply.
Teach "git apply -3" to first check for the trivial merge cases and resolve them without hitting the file-level merge drivers.
Signed-off-by: Jerry Zhang <jerry@skydio.com> [jc: stolen tests from Jerry's patch] Signed-off-by: Junio C Hamano <gitster@pobox.com> ---
apply.c | 21 ++++++++++++++++++ t/t4108-apply-threeway.sh | 45 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 66 insertions(+)
diff --git a/apply.c b/apply.c index 44bc31d6eb..c9f9503e90 100644 --- a/apply.c +++ b/apply.c @@ -3467,6 +3467,21 @@ static int load_preimage(struct apply_state *state, return 0; } +static int resolve_to(struct image *image, const struct object_id *result_id) +{ + unsigned long size; + enum object_type type; + + clear_image(image); + + image->buf = read_object_file(result_id, &type, &size); + if (!image->buf || type != OBJ_BLOB) + die("unable to read blob object %s", oid_to_hex(result_id)); + image->len = size; + + return 0; +} + static int three_way_merge(struct apply_state *state, struct image *image, char *path, @@ -3478,6 +3493,12 @@ static int three_way_merge(struct apply_state *state, mmbuffer_t result = { NULL }; int status; + /* resolve trivial cases first */ + if (oideq(base, ours)) + return resolve_to(image, theirs); + else if (oideq(base, theirs) || oideq(ours, theirs)) + return resolve_to(image, ours); + read_mmblob(&base_file, base); read_mmblob(&our_file, ours); read_mmblob(&their_file, theirs); diff --git a/t/t4108-apply-threeway.sh b/t/t4108-apply-threeway.sh index 65147efdea..cc3aa3314a 100755 --- a/t/t4108-apply-threeway.sh +++ b/t/t4108-apply-threeway.sh @@ -230,4 +230,49 @@ test_expect_success 'apply with --3way --cached and conflicts' ' test_cmp expect.diff actual.diff ' +test_expect_success 'apply binary file patch' ' + git reset --hard main && + cp "$TEST_DIRECTORY/test-binary-1.png" bin.png && + git add bin.png && + git commit -m "add binary file" && + + cp "$TEST_DIRECTORY/test-binary-2.png" bin.png && + + git diff --binary >bin.diff && + git reset --hard && + + # Apply must succeed. + git apply bin.diff +' + +test_expect_success 'apply binary file patch with 3way' ' + git reset --hard main && + cp "$TEST_DIRECTORY/test-binary-1.png" bin.png && + git add bin.png && + git commit -m "add binary file" && + + cp "$TEST_DIRECTORY/test-binary-2.png" bin.png && + + git diff --binary >bin.diff && + git reset --hard && + + # Apply must succeed. + git apply --3way --index bin.diff +' + +test_expect_success 'apply full-index patch with 3way' ' + git reset --hard main && + cp "$TEST_DIRECTORY/test-binary-1.png" bin.png && + git add bin.png && + git commit -m "add binary file" && + + cp "$TEST_DIRECTORY/test-binary-2.png" bin.png && + + git diff --full-index >bin.diff && + git reset --hard && + + # Apply must succeed. + git apply --3way --index bin.diff +' + test_done
-- 2.33.0-408-g8e1aa136b3