[bug] git-ls-files sometimes does not list files with pathspec magic ":(exclude)"

Hi,

It seems git-ls-files has an issue together with certain ":(exclude)" tags.

For example, on NetworkManager's git tree (top-level directory) I run

  git ls-files -- src/platform/ ":(exclude)shared/n-acd"

which wrongly lists not files. It seems to be some relation between the exclude and the search path because a different path/exclude does not exhibit the problem.

I also tested current git-master (72c4083ddf91b489b7b7b812df67ee8842177d98) which has the same issue.

Here is a reproducer (in a container run on Fedora 33/x86_64):

  podman run -ti alpine:latest \
    sh -c '
      apk add git &&
      git clone https://gitlab.freedesktop.org/NetworkManager/NetworkManager.git &&
      cd NetworkManager &&
      git checkout -B tmp cd754680a6a0e35b286d4157269053ccc3996a32 &&
      echo ">>>>>>now BAD1..." &&
      git ls-files -- src/platform/ ":(exclude)shared/n-acd"
      echo ">>>>>>now GOOD1..." &&
      git ls-files -- src/platform/ ":(exclude)shared/c-list"
      echo ">>>>>>now GOOD2..." &&
      git ls-files -- src/platform ":(exclude)shared/n-acd"
      echo ">>>>>>now GOOD3..." &&
      git ls-files -- src/vpn/ ":(exclude)shared/n-acd"
   '

Note that only the first call in the reproducer has the unexpected result.

best, Thomas

Thomas Haller <thaller@redhat.com> writes:

This does look interesting.

$ git ls-files -- src/platform/ ":(exclude)shared/n-acd" $ git ls-files -- src/platform/ ":(exclude)??????/?????" $ git ls-files -- src/platform/ ":(exclude)??????/????" $ git ls-files -- src/platform/ ":(exclude)??????/???" $ git ls-files -- src/platform/ ":(exclude)??????/??" $ git ls-files -- src/platform/ ":(exclude)??????/?"

None of the above gives any output. And the '/' seems to be a red herring. None of the below (where the '/' in the exclude pathspec is replaced with a single '?') gives any output, either.

$ git ls-files -- src/platform/ ":(exclude)????????????" $ git ls-files -- src/platform/ ":(exclude)???????????" $ git ls-files -- src/platform/ ":(exclude)??????????" $ git ls-files -- src/platform/ ":(exclude)?????????" $ git ls-files -- src/platform/ ":(exclude)????????"

But if we add one more "?" to the longuest ones, i.e.

$ git ls-files -- src/platform/ ":(exclude)?????????????" $ git ls-files -- src/platform/ ":(exclude)shared/n-acd?"

we start seeing output.

What is curious is that the longest problematic negative pathspec, "shared/n-acd" or "????????????", have the same length as "src/platform" without the trailing slash.

    "shared/n-acd"
    "src/platform/"
    "????????????"

The rule IIUC is that a path must match one of the positive pathspec and none of the negative pathspec, but it looks as if there is some bogus optimization based on string length.

An experiment.  These ought to do the same as the first exacmple:

$ git ls-files -- src/platform/ ":(exclude)shared/n-ac[d]" $ git ls-files -- src/platform/ ":(exclude)shared/n-[acd][acd][acd]"

but probably because of the character class [d], it seems to defeat/bypass the broken "optimization" and gives what we expect back.

I'll have to go back to the desk where I have a development environment (not an end user enviornment) to dig deeper, but this is intriguing. I'll look more later unless somebody else beats me to it.

Thanks for a report.

On Wed, Jan 13, 2021 at 06:07:56PM -0800, Junio C Hamano wrote:

I dug a little on this earlier this morning, but didn't get far enough to have any confidence that I wasn't barking totally up the wrong tree. But I found the way the "prefix" is passed match_pathspec to be confusing. This seems to make the problem go away: