largefiles: drop "rel" prefix from filename variables The prefixes were meant to indicate that these paths are repo-relative as opposed to absolute. However, that's what the majority of paths in our code base are, so "rel" made me think they were instead cwd-relative. Let's just drop the prefixes. Differential Revision: https://phab.mercurial-scm.org/D5847

branchmap: add some clarifications and clean up flow - Remove indentation where it is not needed. - Swap the subset test branches to follow along logically and put the 'empty' case last. Differential Revision: https://phab.mercurial-scm.org/D5637