`git clean` is destructive and undocumented

[nojnhuh]

I have some gitignored local configuration I maintain locally in the same directory as a git repo. Running go-apidiff irrecoverably deletes all of those files because of the git clean it does here:

go-apidiff/pkg/diff/run.go

Lines 199 to 201 in 00f8d2e

	if err := wt.Clean(&git.CleanOptions{Dir: true}); err != nil {
	return nil, nil, err
	}

This behavior is destructive and essentially impossible to know about until it's too late. This behavior should be documented and put behind a descriptive flag like --force-clean.

[joelanford]

Oh no! Sorry about that!

It took quite a bit of trial and error to make go-apidiff robustly handle various scenarios with what it might encounter in a git tree. The main guard that I thought protected against destructive actions is this IsClean() check:

go-apidiff/pkg/diff/run.go

Lines 80 to 82 in bb5ff5a

	} else if !stat.IsClean() {
	return nil, &GitStatusError{stat, fmt.Errorf("current git tree is dirty")}
	}

It's been quite a long time since I wrote most of this code, and I unfortunately don't even remember why wt.Clean() is called there.

There are definitely some oddities I've encountered with go-git, where it behaves a little bit different to the git CLI, so that might partly explain it.

I don't have a lot of time to work on this project, but I'd definitely be willing to accept a PR that either:

• handles this scenario in a non-destructive way
• adds additional checks for potential destructive actions and just fails out