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@xxxxxxxxxx>
---
Documentation/git-apply.txt | 5 ++---
apply.c | 13 ++++++-------
t/t4108-apply-threeway.sh | 20 ++++++++++++++++++++
3 files changed, 28 insertions(+), 10 deletions(-)
diff --git a/Documentation/git-apply.txt b/Documentation/git-apply.txt
index 91d9a8601c8c316d4649c405af42e531c39991a8..9144575299c264dd299b542b7b5948eef35f211c 100644
--- a/Documentation/git-apply.txt
+++ b/Documentation/git-apply.txt
@@ -84,9 +84,8 @@ OPTIONS
-3::
--3way::
- When the patch does not apply cleanly, fall back on 3-way merge if
- the patch records the identity of blobs it is supposed to apply to,
- and we have those blobs available locally, possibly leaving the
+ Attempt 3-way merge if the patch records the identity of blobs it is supposed
+ to apply to and we have those blobs available locally, possibly leaving the
conflict markers in the files in the working tree for the user to
resolve. This option implies the `--index` option, and is incompatible
with the `--reject` and the `--cached` options.
diff --git a/apply.c b/apply.c
index 6695a931e979a968b28af88d425d0c76ba17d0d4..9bd4efcbced842d2c5c030a0f2178ddb36114600 100644
--- a/apply.c
+++ b/apply.c
@@ -3569,10 +3569,10 @@ static int try_threeway(struct apply_state *state,
write_object_file("", 0, blob_type, &pre_oid);
else if (get_oid(patch->old_oid_prefix, &pre_oid) ||
read_blob_object(&buf, &pre_oid, patch->old_mode))
- return error(_("repository lacks the necessary blob to fall back on 3-way merge."));
+ return error(_("repository lacks the necessary blob to perform 3-way merge."));
if (state->apply_verbosity > verbosity_silent)
- fprintf(stderr, _("Falling back to three-way merge...\n"));
+ fprintf(stderr, _("Performing three-way merge...\n"));
img = strbuf_detach(&buf, &len);
prepare_image(&tmp_image, img, len, 1);
@@ -3604,7 +3604,7 @@ static int try_threeway(struct apply_state *state,
if (status < 0) {
if (state->apply_verbosity > verbosity_silent)
fprintf(stderr,
- _("Failed to fall back on three-way merge...\n"));
+ _("Failed to perform three-way merge...\n"));
return status;
}
@@ -3637,10 +3637,9 @@ static int apply_data(struct apply_state *state, struct patch *patch,
if (load_preimage(state, &image, patch, st, ce) < 0)
return -1;
- if (patch->direct_to_threeway ||
- apply_fragments(state, &image, patch) < 0) {
+ if (!state->threeway || try_threeway(state, &image, patch, st, ce) < 0) {
/* Note: with --reject, apply_fragments() returns 0 */
- if (!state->threeway || try_threeway(state, &image, patch, st, ce) < 0)
+ if (patch->direct_to_threeway || apply_fragments(state, &image, patch) < 0)
return -1;
}
patch->result = image.buf;
@@ -5017,7 +5016,7 @@ int apply_parse_options(int argc, const char **argv,
OPT_BOOL(0, "apply", force_apply,
N_("also apply the patch (use with --stat/--summary/--check)")),
OPT_BOOL('3', "3way", &state->threeway,
- N_( "attempt three-way merge if a patch does not apply")),
+ N_( "attempt three-way merge, fall back on normal patch if that fails")),
OPT_FILENAME(0, "build-fake-ancestor", &state->fake_ancestor,
N_("build a temporary index based on embedded index information")),
/* Think twice before adding "--nul" synonym to this */
diff --git a/t/t4108-apply-threeway.sh b/t/t4108-apply-threeway.sh
index d62db3fbe16f35a625a4a14eebb70034f695d3eb..9ff313f976422f9c12dc8032d14567b54cfe3765 100755
--- a/t/t4108-apply-threeway.sh
+++ b/t/t4108-apply-threeway.sh
@@ -160,4 +160,24 @@ test_expect_success 'apply -3 with add/add conflict (dirty working tree)' '
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
--
2.29.0
