backup: Use new "anything" terminal. This means that content that
is not unused, but has no associated file will be wanted by backup repos.
unwanted: "not anything" will result in any and all content moving
off of these repos.
incremental backup: Remove the "(include=* or unused)",
so it matches content that has no associated files
but is not unused.
client: Add a include=* to the expression. This limits it to matching
only files in the work tree. Without this change, sync --all --content
would match a key against the expression, and since it matches
exclude=archive/*, the client repo would have wanted the file content.
The "and not unused" would have kept unused objects out, but not
objects that were not known to be unused, or objects that another branch
referred to. In practice, everything would have flooded into client repos
without this change.
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