Initial version does not work if pattern is supplied

[jsok]

Effectively, if a pattern is supplied and no existing tags are found an error is always returned.

svu/internal/git/git.go

Lines 45 to 54 in 0b3a780

	g, err := glob.Compile(pattern)
	if err != nil {
	return "", err
	}
	for _, tag := range tags {
	if g.Match(tag) {
	return tag, nil
	}
	}
	return "", fmt.Errorf("no tags match '%s'", pattern)

Whereas if no pattern is supplied, it is not an error to find no tags:

svu/internal/git/git.go

Lines 38 to 40 in 0b3a780

	if len(tags) == 0 {
	return "", nil
	}

[harnash]

I think this is quite useful when working inside monorepo.
This PR #57 looks promising. What needs to happen to have it implemented/fixed?