This is needed because when preferred content matches on files,
the second pass would otherwise want to drop all keys. Using a bloom filter
avoids this, and in the case of a false positive, a key will be left
undropped that preferred content would allow dropping. Chances of that
happening are a mere 1 in 1 million.
This makes git annex unused use around 48 mb more memory than it did before,
but the massive increase in accuracy makes this worthwhile for all but the
smallest systems.
Also, I want to use the bloom filter for sync --all --content, to avoid
dropping files that the preferred content doesn't want, and 1/1000
false positives would be far too many in that use case, even if it were
acceptable for unused.
Actual memory use numbers:
1000: 21.06user 3.42system 0:26.40elapsed 92%CPU (0avgtext+0avgdata 501552maxresident)k
1000000: 21.41user 3.55system 0:26.84elapsed 93%CPU (0avgtext+0avgdata 549496maxresident)k
10000000: 21.84user 3.52system 0:27.89elapsed 90%CPU (0avgtext+0avgdata 549920maxresident)k
Based on these numbers, 10 million seemed a better pick than 1 million.
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.
