From 923cd87ac8550a8e277bfeb19198a11b6a8ed854 Mon Sep 17 00:00:00 2001 From: Jerry Zhang Date: Tue, 6 Apr 2021 16:25:32 -0700 Subject: 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 Signed-off-by: Junio C Hamano diff --git a/Documentation/git-apply.txt b/Documentation/git-apply.txt index 91d9a86..9144575 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 466f880..6919726 100644 --- a/apply.c +++ b/apply.c @@ -3570,10 +3570,10 @@ 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); @@ -3605,7 +3605,7 @@ 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; } @@ -3638,10 +3638,9 @@ 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; @@ -5018,7 +5017,7 @@ 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 d62db3f..9ff313f 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 -- cgit v0.10.2-6-g49f6