wireprotov2: implement command for retrieving raw store files
Implementing shallow clone of the changelog is hard. We want the 4.8
release to have a fast implementation of partial clone in wireprotov2. In
order to achieve fast, we can't use deltas for transferring changelog and
manifestlog data.
Per discussions at the 4.8 sprint, this commit implements a somwwhat hacky
and likely-to-be-changed-drastically-or-dropped command in wireprotov2 that
facilitates access to raw store files, namely the changelog and manifestlog.
Using this command, clients can perform a "stream clone" of sorts for just
the changelog and manifestlog. This will allow clients to fetch the changelog
and manifest revlogs, stream them to disk (which should be fast), then follow
up filesdata requests for files revision data for a particular changeset.
Differential Revision: https://phab.mercurial-scm.org/D5134
Integration with the share extension needs improvement. Right now
we've seen some odd bugs.
Address commentary in manifest.excludedmanifestrevlog.add -
specifically we should improve the collaboration with core so that
add() never gets called on an excluded directory and we can improve
the stand-in to raise a ProgrammingError.
Reason more completely about rename-filtering logic in
narrowfilelog. There could be some surprises lurking there.
Formally document the narrowspec format. For bonus points, unify with the
server-specified narrowspec format.
narrowrepo.setnarrowpats() or narrowspec.save() need to make sure
they're holding the wlock.
The follinwg places do an unrestricted dirstate walk (including files outside the
narrowspec). Some of them should perhaps not do that.
* debugfileset
* perfwalk
* sparse (but restricted to sparse config)
* largefiles