The filtering is fairly efficient as far as building the trees goes,
since it reuses adjustTree. But it still needs to traverse the whole
tree, and look up the keys used by every file.
The tree that gets recorded to export.log is the filtered tree.
This way resumes of interrupted sync to an export uses it without
needing to recalculate it. And, a change to the preferred content
settings of the remote will result in a different tree, so the export
will be updated accordingly.
The original tree is still used in the remote tracking branch.
That branch represents the special remote as a git remote, and if it
were a normal git remote, the tree in its head would not be affected by
preferred content.
Only when the preferred content expression includes them will a parse
failure due to them needing keys result in the preferred content
expression not parsing in keyless mode.
This will let import try to match preferred content expressions before
downloading the content and generating its key.
If an expression needs a key, it preferredContentParser with
preferredContentKeylessTokens will fail to parse it.
standard and groupwanted are not in preferredContentKeylessTokens
because they may refer to an expression that refers to a key.
That needs further work to support them.
Added the ability to run one job per CPU (core), by setting annex.jobs=cpus,
or using option --jobs=cpus or -Jcpus.
Built with future expansion in mind, including not defaulting matching on
Concurrency so more constructors can later be added, and using "cpu"
instead of "0".
