subrepo: abort instead of pushing/pulling to the repo itself _abssource will now abort (or return None) in the rare cases where no push/pull path can be found.

subrepo: rename relpath to subrelpath and introduce reporelpath

mdiff: carriage return (\r) is also ignorable whitespace

merge: add --tool argument to merge and resolve These arguments are shorthand for --config ui.merge, but they also override HGMERGE if it is found in the user's environment.