git ls-tree

Files in tree identified by tag v1.0 at the top level:

$ git ls-tree --name-only tags/v1.0

Files in tree identified by tag v1.0 at all levels:

$ git ls-tree --name-only tags/v1.0 -r

Files in tree identified by tag v1.0 in path foo/bar at all levels:

$ git ls-tree --name-only tags/v1.0 foo/bar -r