diff tests/test-strip.t @ 36971:b89a7ef29013

bundle: include advisory rev branch cache part in bundle2 bundle

`hg bundle` command producing bundle2 will now include an optional part
containing the revision-branch cache data.

The data sent are mostly nodes so it is quite compact.  The goal of the
rev-branch-cache is to speed up branch map computation, especially when the
branchmap gets invalidated so we send data for all exchanged changesets. In
addition, computing the relevant heads to send in case of partial pulling would
be challenging.

As a reminder, the rev branch cache data significantly speed up branch
computation. Having it around provides a small speedup to pull/clone and much
higher tolerance to branch map cache invalidation that might happens from later
commands.

On the Mercurial repository, computing the visible branchmap from scratch move
from 2.00 seconds to 0.34s (a -83% speedup).

Using this new part, Unbundling the full Mercurial repository moves from 25.736
seconds to 24.030 seconds (around -7% speedup). The bundle size increase is
around 3% (from 22.43 MB to 23.13MB)


On an half a million revision repository with twenty thousand
branches, computing the branchmap moves from 75 seconds to 45 second (-40%) if
the caches is used.

A bundle containing 50 000 changesets in such repository get a 0.5% size
increase from such part for a -3% unbundling time speedup.

--- a/tests/test-strip.t	Wed Feb 21 17:26:22 2018 +0100
+++ b/tests/test-strip.t	Wed Feb 21 17:33:00 2018 +0100
@@ -214,6 +214,7 @@
   Stream params: {Compression: BZ}
   changegroup -- {nbchanges: 1, version: 02}
       264128213d290d868c54642d13aeaa3675551a78
+  cache:rev-branch-cache -- {}
   phase-heads -- {}
       264128213d290d868c54642d13aeaa3675551a78 draft
   $ hg pull .hg/strip-backup/*
@@ -843,13 +844,13 @@
   list of changesets:
   6625a516847449b6f0fa3737b9ba56e9f0f3032c
   d8db9d1372214336d2b5570f20ee468d2c72fa8b
-  bundle2-output-bundle: "HG20", (1 params) 2 parts total
+  bundle2-output-bundle: "HG20", (1 params) 3 parts total
   bundle2-output-part: "changegroup" (params: 1 mandatory 1 advisory) streamed payload
+  bundle2-output-part: "cache:rev-branch-cache" streamed payload
   bundle2-output-part: "phase-heads" 24 bytes payload
   saved backup bundle to $TESTTMP/issue4736/.hg/strip-backup/6625a5168474-345bb43d-backup.hg
   updating the branch cache
   invalid branchheads cache (served): tip differs
-  truncating cache/rbc-revs-v1 to 24
   $ hg log -G
   o  changeset:   2:5c51d8d6557d
   |  tag:         tip