| commit | 623f7af28417805d941b1618157b9d93c02347af | [log] [tgz] |
|---|---|---|
| author | Jeff King <peff@peff.net> | Fri Oct 17 04:36:41 2025 -0400 |
| committer | Junio C Hamano <gitster@pobox.com> | Fri Oct 17 11:41:50 2025 -0700 |
| tree | b3fc64acf7676fe1e1d45e3520409b5df7210169 | |
| parent | 1e0a3e8f8f9e160b21fbe6f3f11a11dbed15fb4e [diff] |
diff: restore redirection to /dev/null for diff_from_contents In --quiet mode, since we produce only an exit code for "something was changed" and no actual output, we can often get by with just a tree-level diff. However, certain options require us to actually look at the file contents (e.g., if we are ignoring whitespace changes). We have a flag "diff_from_contents" for that, and if it is set we call diff_flush() on each path. To avoid producing any output (since we were asked to be --quiet), we traditionally just redirected the output to /dev/null. That changed in b55e6d36eb (diff: ensure consistent diff behavior with ignore options, 2025-08-08), which replaced that with a "dry_run" flag. In theory, with dry_run set, we should produce no output. But it carries a risk of regression: if we forget to respect dry_run in any of the output paths, we'll accidentally produce output. And indeed, there is at least one such regression in that commit, as it covered only the case where we actually call into xdiff, and not creation or deletion diffs, where we manually generate the headers. We even test this case in t4035, but only with diff-tree, which does not show the bug by default because it does not require diff_from_contents. But git-diff does, because it allows external diff programs by default (so we must dig into each diff filepair to decide if it requires running an external diff that may declare two distinct blobs to actually be the same). We should fix all of those code paths to respect dry_run correctly, but in the meantime we can protect ourselves more fully by restoring the redirection to /dev/null. This gives us an extra layer of protection against regressions dues to other code paths we've missed. Though the original issue was reported with "git diff" (and due to its default of --ext-diff), I've used "diff-tree -w" in the new test. It triggers the same issue, but I think the fact that "-w" implies diff_from_contents is a bit more obvious, and fits in with the rest of t4035. Reported-by: Jake Zimmerman <jake@zimmerman.io> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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