There is no real concept of a "repository name" in Mercurial (a repository doesn't "know" or care about its own name). I think you mean "last past component of the default pull path"?
If so, then parsing the output of hg path default
would be the most direct way to get that information.
However, you should note that the default path can (and often is) changed: think of cloning a local clone time for testing:
$ hg clone http://server/lib-foo
$ hg clone lib-foo lib-foo-test
$ hg clone lib-foo-test lib-foo-more-testing
The lib-foo-more-testing
clone has a default push path back to lib-foo-test
.
This means that parsing hg paths default
wont be much more reliable than using basename $(hg root)
— both can be completely different from the (base)name of the repository that was originally cloned.
If what you really want is to get an "identity" for a repository, then you should instead use
$ hg log -r 0 --template "{node}"
The first changeset hash in a repository will normally uniquely identify the repository and it will be stable even when clones change names. (If a repository has two or more roots, then the zeroth changeset can in principle differ between clones. People will have to actively try to make it differ, though.)