Re: gitignore + commit with excludes = bug

[Philip Oakley <philipoakley@iee.email>]

Hi Paul,

On 01/05/2021 19:37, Paul Jackson wrote:
> Hello,
>
> I stumbled upon what I believe is a bug in git.
> See the following reproduction steps:
>
> mkdir test
> cd test
> git init
> echo 1 > ignored
> echo 1 > not-ignored
> echo ignored > .gitignore
> git add -A -- ':!ignored' || echo 'ERROR!!!'
>
> In these steps, I ignore the "ignored" file twice - first time in
> .gitignore, and second time in the "git add" command. I didn't expect
> this to be a problem, but I'm getting the following error message:
>
> The following paths are ignored by one of your .gitignore files:
> ignored
>
> It looks as if git thinks I wanted to include, not exclude "ignored"
> in "git add".
I was intrigued by this. The man pages can be hard to decipher, and it
may be an 'as designed' feature, but still not intuitive

It took a while to find the relevant parts of the man pages.

The `-A` option of `add` is under
https://git-scm.com/docs/git-add#Documentation/git-add.txt---no-ignore-removal
which has caveats for whether a pathspec is given.

The `exclude` magic pathspec is under
https://git-scm.com/docs/gitglossary#Documentation/gitglossary.txt-exclude
and again has caveats and a double negative regarding whether the
`exclude` pathspec counts as a path spec.

I _think_ that it is saying that the `exclude` pathspec is ignored for
the purpose of the `-A` (all) condition for git add.
The `git add` then decides that the the set of files to be added is just
the single 'not-ignored' file, having already used the `.gitignore` to
"exclude" the 'ignored' file from that set of files to add.

Now your "exclude" pathspec comes into play and tries remove the named
"exclude" file from the set, and doesn't find it. Or at least that's how
I read it as a plausible explanation. That said, I haven't looked at the
code, so that could be all wrong.

A possible place to start is the
https://gitlab.cecs.anu.edu.au/comp8440/git/commit/ef79b1f8704668a6cdf4278f9255e03ca785bfb4
patch (google..) or
https://github.com/git/git/commit/ef79b1f8704668a6cdf4278f9255e03ca785bfb4

Also locate where the error message is generated. It maybe just a warning.

--
Philip