The `skipflags` config was introduced in a2ab9ebcd85b, which specifically calls
out downloading and storing all blobs as potentially too expensive.  But I don't
see any reason to skip blobs that are already available locally.  Hashing the
blob is the only way to indirectly verify the rawdata content stored in the
revlog.

(The note in that commit about skipping renamed is still correct, but the reason
given about needing fulltext isn't.)

Differential Revision: https://phab.mercurial-scm.org/D7712