update: replace workingctx.dirty and raising Abort by cmdutil.bailifchanged This patch makes wrapping "commands.update()" by largefiles extension useless, because "cmdutil.bailifchanged()" can detect changes of largefiles in the working directory. This patch also changes test-update-branches.t, because "cmdutil.bailifchanged()" shows more detailed information about dirty-ness of the working directory than "workingctx.dirty()".