manifest: document return type of readfast()
I keep having to ponder out what readfast() means, and it always
surprises me. Document the return type in the docstring so that future
readers won't have to puzzle this out again.
requesting all changes
adding changesets
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added 1 changesets with 4 changes to 4 files
updating to branch default
4 files updated, 0 files merged, 0 files removed, 0 files unresolved
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 4 changes to 4 files
updating to branch default
4 files updated, 0 files merged, 0 files removed, 0 files unresolved