narrow: remove custom filelog type
This functionality is now handled by core as of the previous commit.
I wanted this to be a standalone commit because the deleted code
makes a reference to remotefilelog's file type missing a node() method
and this may have implications to narrow+remotefilelog usage. The code
in core doesn't perform this check and therefore behavior may be subtly
different and buggy.
But I /think/ the check is merely a performance optimization and
nothing more. So I'm optimistic this will continue to "just work."
Differential Revision: https://phab.mercurial-scm.org/D4644
Set up
$ hg init repo
$ cd repo
Try to import an empty patch
$ hg import --no-commit - <<EOF
> EOF
applying patch from stdin
abort: stdin: no diffs found
[255]
No dirstate backups are left behind
$ ls .hg/dirstate* | sort
.hg/dirstate