merge with stable

largefiles: remove bailifchanged check from overridepull (BC) This brings pull --rebase with largefiles in line with pull --rebase without.

rebase: remove bailifchanged check from pullrebase (BC) This saves us a relatively superfluous status check for pull --rebase (if rebase runs, it'll check for a clean working directory anyway), and brings hg pull --rebase closer to hg pull && hg rebase. This is a behavior change because pull --rebase with a dirty working directory will now abort after performing the pull rather than before.

debugshell: check ui.debugger for which debugger to use