Merge branch 'ps/remote-rename-fix'

"git remote rename origin upstream" failed to move origin/HEAD to upstream/HEAD when origin/HEAD is unborn and performed other renames extremely inefficiently, which has been corrected. * ps/remote-rename-fix: builtin/remote: only iterate through refs that are to be renamed builtin/remote: rework how remote refs get renamed builtin/remote: determine whether refs need renaming early on builtin/remote: fix sign comparison warnings refs: simplify logic when migrating reflog entries refs: pass refname when invoking reflog entry callback