@matheusbsbs / matheus-bagliano / commits / e1d3d61a45

diff: --no-index should ignore the worktree

The act of giving "--no-index" tells Git to pretend that the current directory is not under control of any Git index or repository, so even when you happen to be in a Git controlled working tree, where in that working tree should not matter. But the start-up sequence tries to discover the top of the working tree and chdir(2)'s there, even before Git passes control to the subcommand being run. When diff_no_index() starts running, it starts at a wrong (from the end-user's point of view who thinks "git diff --no-index" is merely a better version of GNU diff) directory, and the original directory the user started the command is at "prefix". Because the paths given from argv[] have already been adjusted to account for this path shuffling by prepending the prefix, and showing the resulting path by stripping the prefix, the effect of these nonsense operations (nonsense in the context of "--no-index", that is) is usually not observable. Except for special cases like "-", where it is not preprocessed by prepending the prefix. Instead of papering over by adding more special cases only to cater to the no-index codepath in the generic code, drive the diff machinery more faithfully to what is going on. If the user started "git diff --no-index" in directory X/Y/Z in a working tree controlled by Git, and the start up sequence of Git chdir(2)'ed up to directory X and left Y/Z in the prefix, revert the effect of the start up sequence by chdir'ing back to Y/Z and emptying the prefix. Reported-by: Gregoire Geis <opensource@gregoirege.is> Helped-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Junio C Hamano committed Aug 9, 2025 at 17:20 UTC e1d3d61a45bfdc5031d2066c0e4505ebd8145777

2 files changed +32

builtin/diff.c

+15

@@ -487,6 +487,21 @@ int cmd_diff(int argc,

487

488 init_diff_ui_defaults();

489 repo_config(the_repository, git_diff_ui_config, NULL);

490 +

491 + /*

492 + * If we are ignoring the fact that our current directory may

493 + * be part of a working tree controlled by a Git repository to

494 + * pretend to be a "better GNU diff", we should undo the

495 + * effect of the setup code that did a chdir() to the top of

496 + * the working tree. Where we came from is recorded in the

497 + * prefix.

498 + */

499 + if (no_index && prefix) {

500 + if (chdir(prefix))

501 + die(_("cannot come back to cwd"));

502 + prefix = NULL;

503 + }

504 +

505 prefix = precompose_argv_prefix(argc, argv, prefix);

506

507 repo_init_revisions(the_repository, &rev, prefix);

t/t4053-diff-no-index.sh

+17

@@ -26,6 +26,23 @@ test_expect_success 'git diff --no-index directories' '

26 test_line_count = 14 cnt

27 '

29 +test_expect_success 'git diff --no-index with -' '

30 + cat >expect <<-\EOF &&

31 + diff --git a/- b/-

32 + new file mode 100644

33 + --- /dev/null

34 + +++ b/-

35 + @@ -0,0 +1 @@

36 + +frotz

37 + EOF

38 + (

39 + cd a &&

40 + echo frotz |

41 + test_expect_code 1 git diff --no-index /dev/null - >../actual

42 + ) &&

43 + test_cmp expect actual

44 +'

45 +

46 test_expect_success 'git diff --no-index relative path outside repo' '

47 (

48 cd repo &&