filemerge: set default labels a little earlier
By setting the default labels a little earlier, we can rely on them
always being set, as far as I can tell. It may actually even be fine
to rely on that even if we don't set them earlier, but it makes more
sense to me to do it.
Differential Revision: https://phab.mercurial-scm.org/D12015
$ 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