[RFC] builtin/stash: data loss from reset --hard

Hi,

I am a beginner C developer exploring the Git codebase and came across something I would like to understand better.

In builtin/stash.c line 1747, there is a comment:

    /* BUG: this nukes untracked files in the way */
    strvec_pushl(&cp.args, "reset", "--hard", "-q",
                 "--no-recurse-submodules", NULL);

Steps to reproduce:

    $ git init test && cd test
    $ echo "tracked" > foo && git add foo && git commit -m "init"
    $ git rm foo
    $ mkdir foo && echo "precious" > foo/file
    $ git stash
    $ cat foo/file
    cat: foo/file: Not a directory   # precious data is lost

The reset --hard restores the original tracked file "foo" from HEAD, destroying the untracked directory "foo/" and its contents.

There is also a test_expect_failure test in t/t2500-untracked-overwriting.sh that documents this behavior.

I am not sure if this is considered a bug to be fixed, or intentional behavior that is simply documented.

If it is a bug, would this fix be reasonable:

-       /* BUG: this nukes untracked files in the way */
-       strvec_pushl(&cp.args, "reset", "--hard", "-q",
+       strvec_pushl(&cp.args, "reset", "--merge", "-q",
                     "--no-recurse-submodules", NULL);

I understand --merge would fail instead of silently overwriting, which seems safer.

I would appreciate any feedback or guidance.

Thanks, Tsahi

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