Fix missing blank repository name when cloning

If the repository path given to 'vcsh clone' contains a trailing slash,
the resulting cloned directory will be '.git' and vcsh will not
recognize the cloned repository by name. This change ensures that a
trailing slash will be stripped and the repository name will be
populated.

The previous faulty behavior is due to the custom implementation of the
basename command first introduced in 794f0aac.
Merge remote-tracking branch 'archwyrm/clone-trailing-slash-fix'
Revert "Implement basename in shell"

This reverts commit 794f0aac869dda034300211e9be45db123d84377.

Conflicts:
	vcsh

Turns out the shell implementation didn't account for trailing
slashes. While, arguably, a proper interactive shell should eat
them before execution anyway, this can also be called in script
context.

This means that

    vcsh clone foo/

made it fail and even after commit 7e33e38a869989d04d12f2ef160d514041eb01e3

    vcsh clone foo//

would have failed.

Revert to safe and time-proven default: Standalone `basename`.

For further information, see:

https://github.com/RichiH/vcsh/pull/92