Re: [PATCH v3 1/5] t3701: redefine what is "bogus" output of a diff filter

> On Wed, Aug 31, 2022 at 11:36:19AM -0400, Jeff King wrote:
>
> > > I'm struggling to understand the need for this change from the explanation
> > > in the commit message as it seems to me  to assume the line being deleted is
> > > the hunk header when in fact it is deleting the diff header.
> >
> > FWIW, as the author of the original test, I'm also confused about why it
> > needs to be changed. The filter I wrote in the original test was just
> > "echo too-short". It was switched to "sed 1d" because the original did
> > not read the input at all, which racily caused Git to see SIGPIPE:
> >
> >   https://lore.kernel.org/git/20200113170417.GK32750@szeder.dev/
> >
> > Switching to "exit 0" would bring that problem back. But I think "sed q"
> > potentially does, too, because sed will quit without reading all of the
> > input. We really do want something like "sed 1d" that changes the number
> > of lines, but ensures that the filter reads to EOF.
>
> By the way, the test change is needed for it to pass with the change in
> patch 2, where we become more lenient about parsing the hunk header.
> That implies to me that the builtin version's check for one-to-one line
> correspondence is broken, but we didn't notice.

> In the perl version, that test fails because it triggers the
> mismatched-output check:
>
>   $ GIT_TEST_ADD_I_USE_BUILTIN=false ./t3701-add-interactive.sh --verbose-only=56
>   [...]
>   fatal: mismatched output from interactive.diffFilter
>   hint: Your filter must maintain a one-to-one correspondence
>   hint: between its input and output lines.
>   ok 56 - detect bogus diffFilter output
>
> but the builtin version complains about the hunk header:
>
>   $ GIT_TEST_ADD_I_USE_BUILTIN=true ./t3701-add-interactive.sh --verbose-only=56
>   [...]
>   error: could not parse colored hunk header '?[31m-10?[m'
>   ok 56 - detect bogus diffFilter output
>
> Once patch 2 is applied, we stop complaining there, and we _should_
> complain that the number of lines isn't the same. But we don't:
>
>   $ GIT_TEST_ADD_I_USE_BUILTIN=true ./t3701-add-interactive.sh --verbose-only=56
>   test_must_fail: command succeeded: git add -p
>   not ok 56 - detect bogus diffFilter output