test: drop all the forced use of bundle2 Using bundle2 during exchange is now the default, we do not need all this explicit enabling of bundle2 exchange in test anymore.

bundle2: use bundle2 by default All the test change have been isolated and validated. We have free to turn on bundle2 as the default exchange protocol. "To reach a port we must set sail – Sail, not tie at anchor Sail, not drift."

wireprotocol: distinguish list and set in getbundle argument The 'bundlecaps' argument is expected to be a set, but 'listkeys' is expected to be a list where ordering matters. We introduce a new 'scsv' argument type for the 'set' version and move 'csv' to the 'list' version. 'test-ssh.t' is changed because this introduced an instability in the order we were producing listkeys parts.

exchange: support transferring .hgtags fnodes mapping On Mozilla's mozilla-beta repository .hgtags fnodes resolution takes ~18s from a clean cache on my machine. This means that the first time a user runs `hg tags`, `hg log`, or any other command that displays or accesses tags data, a ~18s pause will occur. There is no output during this pause. This results in a poor user experience and perception that Mercurial is slow. The .hgtags changeset to filenode mapping is deterministic. This patch takes advantage of that property by implementing support for transferring .hgtags filenodes mappings in a dedicated bundle2 part. When a client advertising support for the "hgtagsfnodes" capability requests a bundle, a mapping of changesets to .hgtags filenodes will be sent to the client. Only mappings of head changesets included in the bundle will be sent. The transfer of this mapping effectively eliminates one time tags cache related pauses after initial clone. The mappings are sent as binary data. So, 40 bytes per pair of SHA-1s. On the aforementioned mozilla-beta repository, 659 * 40 = 26,360 raw bytes of mappings are sent over the wire (in addition to the bundle part headers). Assuming 18s to populate the cache, we only need to transfer this extra data faster than 1.5 KB/s for overall clone + tags cache population time to be shorter. Put into perspective, the mozilla-beta repository is ~1 GB in size. So, this additional data constitutes <0.01% of the cloned data. The marginal overhead for a multi-second performance win on clones in my opinion justifies an on-by-default behavior.

bundle2: part handler for processing .hgtags fnodes mappings .hgtags fnodes cache entries can be expensive to compute, especially if there are hundreds of even thousands of them. This patch implements support for receiving a bundle2 part that contains a mapping of changeset to .hgtags fnodes. An upcoming patch will teach the server to send this part, allowing clients to bypass having to redundantly compute these values. A number of tests changed due to the client advertising the "hgtagsfnodes" capability.

changegroup: rename _computeoutgoing to computeoutgoing We're going to use this function from another module in an upcoming patch. Drop the _ prefix to mark it as non-private.

merge with stable