lfs: add the '{oid}' template keyword to '{lfs_files}'
The 'sha256:' prefix is skipped because this seems like the most convenient way
to consume it. Maybe we should also add a '{oid_type}' keyword? Then again,
that can be added in the future if a different algorithm is supported.
$ rm -rf a
$ hg init a
$ cd a
$ echo a > a
$ hg ci -Am0
adding a
$ hg tag t1 # 1
$ hg tag --remove t1 # 2
$ hg co 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg tag -f -r0 t1
$ hg tags
tip 3:a49829c4fc11
t1 0:f7b1eb17ad24
$ cd ..