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.
$ hg init
$ echo 123 > a
$ hg add a
$ hg commit -m "first" a
$ mkdir sub
$ echo 321 > sub/b
$ hg add sub/b
$ hg commit -m "second" sub/b
$ cat sub/b
321
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat sub/b 2>/dev/null || echo "sub/b not present"
sub/b not present
$ test -d sub || echo "sub not present"
sub not present