[BUG] git add . after removing .git/ in a subdirectory triggers assertion failure

Hi,

No time to debug this for now, but I have a reproduction script:

mkdir test && cd test git init sub cd sub/ touch foo && git add . && git commit -m"foo" cd .. git init git add sub rm -fr sub/.git/ cd sub/ git add .

In short, sub used to be a submodule, but we removed the .git/ and tried to "git add ." the result.

The last line triggers this:

git: pathspec.c:317: prefix_pathspec: Assertion `item->nowildcard_len <= item->len && item->prefix <= item->len' failed.

Cheers,