git filter bug

[mlucool]

There is a bug in git status that happens when a file changes but the filtered version of the file does not. Correctly, git diff does not show anything as different and git commit believes there is nothing to commit.

Reproducer:

$ git init
$ touch bar
$ git add bar
$ git commit -am 'Bar'
[main (root-commit) dd12b3e] Bar
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 bar
$ echo -en '\n[filter "noat"]\n     clean = grep -v "@"\n' >> .git/config
$ cat .git/config 
[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true

[filter "noat"]
     clean = grep -v "@"
$ echo -en 'abc\n@def\nghi\n' > bar 
$ cat bar 
abc
@def
ghi
$ echo "* filter=noat" > .gitattributes
$ git commit -am 'No at bar'
[main e81ee3b] No at bar
 2 files changed, 3 insertions(+)
 create mode 100644 .gitattributes
$ git show HEAD:bar
abc
ghi
$ echo -en 'abc\n@@def\nghi\n' > bar # Add another @ to the same filtered out line. touch doesn't cause this bug
$ git status --porcelain
 M bar
$ git diff # no output as there is no diff
$ git commit -am "I did not update"
On branch main
nothing to commit, working tree clean

While this reproducer is a bit contrived, the real world examples are with Jupyter notebooks filtering output, so I expect this is a somewhat common occurrence.

[dscho]

The issue tracker of the GitGitGadget fork is intended to be used for project ideas (e.g. Outreachy, Google Summer of Code, etc).

The Git project expects bug reports on the Git mailing list (send plain-text messages, HTML messages are dropped silently) instead.

[dscho]

For lurkers, this was indeed reported to the correct list.