remotefilelog: rename wireproto methods and remaining capabilities This is a mess, in part because there should be more constants throughout. I know we typically do exp- instead of the x_ business in this change, but I also had to use this in some function names, so I figured until I can break that coupling I'd go with this. If it's too unpleasant during review, let me know and I can probably clean it up some more. # no-check-commit due to new foo_bar naming - too hard to avoid right now :( Differential Revision: https://phab.mercurial-scm.org/D5129

remotefilelog: consolidate and rename on-disk store requirement The value of this constant appeared in too many places. While we're here, rename it to be more consistent with our naming conventions for experimental functionality. Differential Revision: https://phab.mercurial-scm.org/D5128

remotefilelog: consolidate and rename bundle2 capability Bonus: we catch a spot where the shallowrepo requirement was being misused as the bundle2 capability. Differential Revision: https://phab.mercurial-scm.org/D5127

remotefilelog: rename capability for legacy ssh file fetching method I think I want to delete this, but for now we'll just rename this so it's easy to tell apart from other strings that have the same value. Differential Revision: https://phab.mercurial-scm.org/D5126

remotefilelog: rip out lz4 support Some methods are left teased out so it's easier to build a migration extension from v1 packs to v2. I also anticipate those methods will be of use if we get around to adding configurable compression engines before we end up jettisoning packs. I think it would make sense to register one-shot `compress` and `decompress` methods on our compression engines in util.py, but indygreg mentioned that might not be straightforward. Differential Revision: https://phab.mercurial-scm.org/D4944

remotefilelog: bump pack file formats to version 2 Drop support for format 0 and 1 packs. Version 2 will be different in that it'll use zlib compression instead of lz4, as the latter isn't really suitable for core. If I can make it work, I'll make compression engines pluggable, but the logic for handling these files is spread out enough it's a little tricky to get that right. Test changes are only due to pack files being renamed. The contents of the packs are the same. Differential Revision: https://phab.mercurial-scm.org/D4943

remotefilelog: avoid hard-coding pack names in tests I'm about to alter the pack format, which alters the content-addressed name of the pack file. In order to reduce my own confusion I found it helpful to use an ls | head pipeline since we always want to inspect the newest pack. Differential Revision: https://phab.mercurial-scm.org/D4942

remotefilelog: remove now-unused wirepack code Differential Revision: https://phab.mercurial-scm.org/D5124

remotefilelogserver: remove pack-serving functionality Differential Revision: https://phab.mercurial-scm.org/D5123

remotefilelog: remove support for fetching packs We've never used this at Google, and it's strictly an optimization that indygreg and I are confident we can handle more elegantly later. Let's rip it out to keep the surface area of the imported remotefilelog small. Some tests have changes because the tests for regular packs and repacking were mixed with tests of fetching packs. I'm pretty sure I've done the right thing here. Differential Revision: https://phab.mercurial-scm.org/D5122