Hard reset can leave behind empty directories in the working copy

[mbohy]

This is easiest explained with an example using the git CLI:

❯ git init
Initialized empty Git repository in /private/tmp/go-git-reset/.git/

❯ git commit --allow-empty -m "Initial commit"
[main (root-commit) 34a2ae3] Initial commit

❯ mkdir -p dir1/dir2
❯ echo 'file1' > dir1/dir2/file1

❯ tree dir1
dir1
└── dir2
    └── file1

2 directories, 1 file

❯ cat dir1/dir2/file1
file1

❯ git add dir1
❯ git commit -m "Add dir1"
[main 8bc6548] Add dir1
 1 file changed, 1 insertion(+)
 create mode 100644 dir1/dir2/file1

❯ git status
On branch main
nothing to commit, working tree clean

❯ git reset --hard HEAD^
HEAD is now at 34a2ae3 Initial commit

❯ ls dir1
ls: dir1: No such file or directory

This all behaves as you'd expect: at the end, dir1 and everything under it is gone. If you use go-git to do the hard reset, dir1 will remain.

[mbohy]

The reason this happens is visible here:

go-git/worktree.go

Lines 923 to 942 in 5dabd83

	func rmFileAndDirIfEmpty(fs billy.Filesystem, name string) error {
	if err := util.RemoveAll(fs, name); err != nil {
	return err
	}
	dir := filepath.Dir(name)
	return doCleanDirectories(fs, dir)
	}
	// doCleanDirectories removes empty subdirs (without files)
	func doCleanDirectories(fs billy.Filesystem, dir string) error {
	files, err := fs.ReadDir(dir)
	if err != nil {
	return err
	}
	if len(files) == 0 {
	return fs.Remove(dir)
	}
	return nil
	}

Following the example above, we would be deleting dir1/dir2/file1, so that would be name. Then we get the containing directory of file1, which is dir2, and check if it is empty. It is, so we delete it. However, dir1 doesn't have any files to remove. It only has a subdirectory, dir2. Therefore, there is no opportunity to delete dir1, and it is left in the working copy.