git/t/t4020-diff-external.sh, branch jch

diff: send external diff output to diff_options.file

2025-10-24T17:15:21Z

Diff output usually goes to the process stdout, but it can be redirected with the "--output" option. We store this in the "file" pointer of diff_options, and all of the diff code should write there instead of to stdout. But there's one spot we missed: running an external diff cmd. We don't redirect its output at all, so it just defaults to the stdout of the parent process. We should instead point its stdout at our output file. There are a few caveats to watch out for when doing so: - The stdout field takes a descriptor, not a FILE pointer. We can pull out the descriptor with fileno(). - The run-command API always closes the stdout descriptor we pass to it. So we must duplicate it (otherwise we break the FILE pointer, since it now points to a closed descriptor). - We don't need to worry about closing our dup'd descriptor, since the point is that run-command will do it for us (even in the case of an error). But we do need to make sure we skip the dup() if we set no_stdout (because then run-command will not look at it at all). - When the output is going to stdout, it would not be wrong to dup() the descriptor, but we don't need to. We can skip that extra work with a simple pointer comparison. - It seems like you'd need to fflush() the descriptor before handing off a copy to the child process to prevent out-of-order writes. But that was true even before this patch! It works because run-command always calls fflush(NULL) before running the child. The new test shows the breakage (and fix). The need for duplicating the descriptor doesn't need a new test; that is covered by the later test "GIT_EXTERNAL_DIFF with more than one changed files". Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

t: refactor tests depending on Perl transliteration operator

2025-04-07T21:47:38Z

We have a bunch of tests that use Perl to perform character transliteration via the "y/" or "tr/" operator. These usecases can be trivially replaced with tr(1). Refactor the tests accordingly so that we can drop a couple of PERL_TEST_HELPERS prerequisites. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

t: introduce PERL_TEST_HELPERS prerequisite

2025-04-07T21:47:37Z

In the early days of Git, Perl was used quite prominently throughout the project. This has changed significantly as almost all of the executables we ship nowadays have eventually been rewritten in C. Only a handful of subsystems remain that require Perl: - gitweb, a read-only web interface. - A couple of scripts that allow importing repositories from GNU Arch, CVS and Subversion. - git-send-email(1), which can be used to send mails. - git-request-pull(1), which is used to request somebody to pull from a URL by sending an email. - git-filter-branch(1), which uses Perl with the `--state-branch` option. This command is typically recommended against nowadays in favor of git-filter-repo(1). - Our Perl bindings for Git. - The netrc Git credential helper. None of these subsystems can really be considered to be part of the "core" of Git, and an installation without them is fully functional. It is more likely than not that an end user wouldn't even notice that any features are missing if those tools weren't installed. But while Perl nowadays very much is an optional dependency of Git, there is a significant limitation when Perl isn't available: developers cannot run our test suite. Preceding commits have started to lift this restriction by removing the strict dependency on Perl in many central parts of the test library. But there are still many tests that rely on small Perl helpers to do various different things. Introduce a new PERL_TEST_HELPERS prerequisite that guards all tests that require Perl. This prerequisite is explicitly different than the preexisting PERL prerequisite: - PERL records whether or not features depending on the Perl interpreter are built. - PERL_TEST_HELPERS records whether or not a Perl interpreter is available for our tests. By having these two separate prerequisites we can thus distinguish between tests that inherently depend on Perl because the underlying feature does, and those tests that depend on Perl because the test itself is using Perl. Adapt all tests to set the PERL_TEST_HELPERS prerequisite as needed. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

t: remove TEST_PASSES_SANITIZE_LEAK annotations

2024-11-20T23:23:48Z

Now that the default value for TEST_PASSES_SANITIZE_LEAK is `true` there is no longer a need to have that variable declared in all of our tests. Drop it. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

t: remove unneeded !SANITIZE_LEAK prerequisites

2024-11-20T23:23:47Z

We have a couple of !SANITIZE_LEAK prerequisites for tests that used to fail due to memory leaks. These have all been fixed by now, so let's drop the prerequisite. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

diff: let external diffs report that changes are uninteresting

2024-06-10T16:20:46Z

The options --exit-code and --quiet instruct git diff to indicate whether it found any significant changes by exiting with code 1 if it did and 0 if there were none. Currently this doesn't work if external diff programs are involved, as we have no way to learn what they found. Add that ability in the form of the new configuration options diff.trustExitCode and diff..trustExitCode and the environment variable GIT_EXTERNAL_DIFF_TRUST_EXIT_CODE. They pair with the config options diff.external and diff..command and the environment variable GIT_EXTERNAL_DIFF, respectively. The new options are off by default, keeping the old behavior. Enabling them indicates that the external diff returns exit code 1 if it finds significant changes and 0 if it doesn't, like diff(1). The name of the new options is taken from the git difftool and mergetool options of similar purpose. (There they enable passing on the exit code of a diff tool and to infer whether a merge done by a merge tool is successful.) The new feature sets the diff flag diff_from_contents in diff_setup_done() if we need the exit code and are allowed to call external diffs. This disables the optimization that avoids calling the program with --quiet. Add it back by skipping the call if the external diff is not able to report empty diffs. We can only do that check after evaluating the file-specific attributes in run_external_diff(). If we do run the external diff with --quiet, send its output to /dev/null. I considered checking the output of the external diff to check whether its empty. It was added as 11be65cfa4 (diff: fix --exit-code with external diff, 2024-05-05) and quickly reverted, as it does not work with external diffs that do not write to stdout. There's no reason why a graphical diff tool would even need to write anything there at all. I also considered using a non-zero exit code for empty diffs, which could be done without adding new configuration options. We'd need to disable the optimization that allows git diff --quiet to skip calling external diffs, though -- that might be quite surprising if graphical diff programs are involved. And assigning the opposite meaning of the exit codes compared to diff(1) and git diff --exit-code to the external diff can cause unnecessary confusion. Suggested-by: Phillip Wood Signed-off-by: René Scharfe Signed-off-by: Junio C Hamano

t4020: test exit code with external diffs

2024-06-10T16:19:20Z

Add tests to check the exit code of git diff with its options --quiet and --exit-code when using an external diff program. Currently we cannot tell whether it found significant changes or not. While at it, document briefly that --quiet turns off execution of external diff programs because that behavior surprised me for a moment while writing the tests. Signed-off-by: René Scharfe Signed-off-by: Junio C Hamano

Merge branch 'rs/external-diff-with-exit-code'

2024-05-16T17:09:23Z

* rs/external-diff-with-exit-code: Revert "diff: fix --exit-code with external diff"

Revert "diff: fix --exit-code with external diff"

2024-05-16T17:08:35Z

This reverts commit 11be65cfa43416219e85384a3a80d672b65b76ba, per original author's request to come up with a better strategy.

Merge branch 'rs/external-diff-with-exit-code'

2024-05-15T16:52:54Z

The "--exit-code" option of "git diff" command learned to work with the "--ext-diff" option. * rs/external-diff-with-exit-code: diff: fix --exit-code with external diff diff: report unmerged paths as changes in run_diff_cmd()