histedit: don't clobber working copy on --abort if not on histedit cset...
histedit: don't clobber working copy on --abort if not on histedit cset
Similar to issue4009, 2.7 will force people to abort histedits before
doing interesting things. Without this fix, people with histedit
sessions they wandered away from before upgrading to 2.7 could clobber
their working copy for no reason.
