bundle2: store changeset count when creating file bundles The bundle2 changegroup part has an advisory param saying how many changesets are in the part. Before this patch, we were setting this part when generating bundle2 parts via the wire protocol but not when generating local bundle2 files. A side effect of not setting the changeset count part is that progress bars don't work when applying changesets. As the tests show, this impacted clone bundles, shelve, backup bundles, `hg unbundle`, and anything touching bundle2 files. This patch adds a backdoor to allow us to pass state from changegroup generation into the unbundler. We store the number of changesets in the changegroup in this state and use it to populate the aforementioned advisory part parameter when generating the bundle2 bundle. I concede that I'm not thrilled by how state is being passed in changegroup.py (it feels a bit hacky). I would love to overhaul the rather confusing set of functions in changegroup.py with something that passes rich objects around instead of e.g. low-level generators. However, given the code freeze for 3.9 is imminent, I'd rather not undertake this endeavor right now. This feels like the easiest way to get the parameter added to the changegroup part.

This test file aims at test topological iteration and the various configuration it can has.

  $ cat >> $HGRCPATH << EOF
  > [ui]
  > logtemplate={rev}\n
  > EOF

On this simple example, all topological branch are displayed in turn until we
can finally display 0. this implies skipping from 8 to 3 and coming back to 7
later.

  $ hg init test01
  $ cd test01
  $ hg unbundle $TESTDIR/bundles/remote.hg
  adding changesets
  adding manifests
  adding file changes
  added 9 changesets with 7 changes to 4 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)

  $ hg log -G
  o  8
  |
  | o  7
  | |
  | o  6
  | |
  | o  5
  | |
  | o  4
  | |
  o |  3
  | |
  o |  2
  | |
  o |  1
  |/
  o  0
  

(display all nodes)

  $ hg log -G -r 'sort(all(), topo)'
  o  8
  |
  o  3
  |
  o  2
  |
  o  1
  |
  | o  7
  | |
  | o  6
  | |
  | o  5
  | |
  | o  4
  |/
  o  0
  

(revset skipping nodes)

  $ hg log -G --rev 'sort(not (2+6), topo)'
  o  8
  |
  o  3
  :
  o  1
  |
  | o  7
  | :
  | o  5
  | |
  | o  4
  |/
  o  0
  

(begin) from the other branch

  $ hg log -G -r 'sort(all(), topo, topo.firstbranch=5)'
  o  7
  |
  o  6
  |
  o  5
  |
  o  4
  |
  | o  8
  | |
  | o  3
  | |
  | o  2
  | |
  | o  1
  |/
  o  0