patch: generalize the use of patchmeta in applydiff()
- Add patchmeta.copy() and emit copies from iterhunks. Modifying patchmeta
instances in applydiff() makes things simpler.
- Rename selectfile() into makepatchmeta(). It is responsible for creating
patchmeta for regular patches.
- Pass patchmeta objects to patchfile() directly
patchmeta instances were associated with git patches, for regular patches we
had to pass additional variables to tell the patch intent to patchfile().
Instead, we generate patchmeta for regular patches and pass them. This will
also help with patch filtering by matcher objects.
[ original upstream message ]