setup: make the version computation process more resistant The tag fetching might return and empty string¹, from there everything derails quickly. As setup tools becomes more picky about version format we make the whole seems a bit more robust. The resulting version will be obviously weird, but at least it will actually install itself. [1] This is a problem we will address in the next changesets.

bundlerepo: enforce the requirements declared by the underlying repository Previously, `hg log -r 'bundle()' -R bundle.hg` was failing for me when run from source, complaining about an unknown parent, when the system installed `hg` didn't. Some debugging showed the index was 0 length. It turned out that I didn't have the C extensions compiled, which a simple `hg log -r .` was able to indicate. The problem being that the RequirementError got handled by RepoError, which uses an empty directory as a fallback to process the bundle.

scmutil: make checknewlabel() allow "_" in otherwise numeric names (issue6737)