import: add --bypass option
This feature is more a way to test patching without a working directory than
something people asked about. Adding a --rev option to specify the parent patch
revision would make it a little more useful.
What this change introduces is patch.repobackend class which let patches be
applied against repository revisions. The caller must supply a filestore object
to receive patched content, which can be turned into a memctx with
patch.makememctx() helper.
$ 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