lfs: respect narrowmatcher when testing to add 'lfs' requirement (issue5794) There's a similar test in lfs.wrapper.convertsink(), but I didn't update that because I don't think that the sink repo in a convert can be narrow. It seems reasonable that a narrow clone of an LFS repo may not necessarily be an LFS repo. The only potential issue is that LFS has a hard requirement for changegroup v3, which that extension enables. The use of treemanifest will enable changegroup v3 in narrow clones, because allsupportedversions() in changegroup.py preserves it when it sees a 'treemanifest' requirement. But I don't see where changegroup v3 is enabled for a flat manifest.