tests/test-revset-outgoing.t

dirstate-tree: Fold "tracked descendants" counter update in main walk

For the purpose of implementing `has_tracked_dir` (which means "has tracked
descendants) without an expensive sub-tree traversal, we maintaing a counter
of tracked descendants on each "directory" node of the tree-shaped dirstate.

Before this changeset, mutating or inserting a node at a given path would
involve:

* Walking the tree from root through ancestors to find the node or the spot
  where to insert it
* Looking at the previous node if any to decide what counter update is needed
* Performing any node mutation
* Walking the tree *again* to update counters in ancestor nodes

When profiling `hg status` on a large repo, this second walk takes times
while loading a the dirstate from disk.

It turns out we have enough information to decide before he first tree walk
what counter update is needed. This changeset merges the two walks, gaining
~10% of the total time for `hg update` (in the same hyperfine benchmark as
the previous changeset).

---

Profiling was done by compiling with this `.cargo/config`:

    [profile.release]
    debug = true

then running with:

    py-spy record -r 500 -n -o /tmp/hg.json --format speedscope -- \
    ./hg status -R $REPO --config experimental.dirstate-tree.in-memory=1

then visualizing the recorded JSON file in https://www.speedscope.app/

Differential Revision: https://phab.mercurial-scm.org/D10554

  $ cat >> $HGRCPATH <<EOF
  > [alias]
  > tlog = log --template "{rev}:{node|short}: '{desc}' {branches}\n"
  > tglog = tlog -G
  > tout = out --template "{rev}:{node|short}: '{desc}' {branches}\n"
  > EOF

  $ hg init a
  $ cd a

  $ echo a > a
  $ hg ci -Aqm0

  $ echo foo >> a
  $ hg ci -Aqm1

  $ hg up -q 0

  $ hg branch stable
  marked working directory as branch stable
  (branches are permanent and global, did you want a bookmark?)
  $ echo bar >> a
  $ hg ci -qm2

  $ hg tglog
  @  2:7bee6c3bea3a: '2' stable
  |
  | o  1:3560197d8331: '1'
  |/
  o  0:f7b1eb17ad24: '0'
  

  $ cd ..

  $ hg clone -q a#stable b

  $ cd b
  $ cat .hg/hgrc
  # example repository config (see 'hg help config' for more info)
  [paths]
  default = $TESTTMP/a#stable
  
  # path aliases to other clones of this repo in URLs or filesystem paths
  # (see 'hg help config.paths' for more info)
  #
  # default:pushurl = ssh://[e-mail]/hg/jdoes-fork
  # my-fork         = ssh://[e-mail]/hg/jdoes-fork
  # my-clone        = /home/jdoe/jdoes-clone
  
  [ui]
  # name and email (local to this repository, optional), e.g.
  # username = Jane Doe <[e-mail]>

  $ echo red >> a
  $ hg ci -qm3

  $ hg up -q default

  $ echo blue >> a
  $ hg ci -qm4

  $ hg tglog
  @  3:f0461977a3db: '4'
  |
  | o  2:1d4099801a4e: '3' stable
  | |
  | o  1:7bee6c3bea3a: '2' stable
  |/
  o  0:f7b1eb17ad24: '0'
  

  $ hg tout
  comparing with $TESTTMP/a
  searching for changes
  2:1d4099801a4e: '3' stable

  $ hg tlog -r 'outgoing()'
  2:1d4099801a4e: '3' stable

  $ hg tout ../a#default
  comparing with ../a
  searching for changes
  3:f0461977a3db: '4' 

  $ hg tlog -r 'outgoing("../a#default")'
  3:f0461977a3db: '4' 

  $ echo "green = ../a#default" >> .hg/hgrc

  $ cat .hg/hgrc
  # example repository config (see 'hg help config' for more info)
  [paths]
  default = $TESTTMP/a#stable
  
  # path aliases to other clones of this repo in URLs or filesystem paths
  # (see 'hg help config.paths' for more info)
  #
  # default:pushurl = ssh://[e-mail]/hg/jdoes-fork
  # my-fork         = ssh://[e-mail]/hg/jdoes-fork
  # my-clone        = /home/jdoe/jdoes-clone
  
  [ui]
  # name and email (local to this repository, optional), e.g.
  # username = Jane Doe <[e-mail]>
  green = ../a#default

  $ hg tout green
  abort: repository green does not exist
  [255]

  $ hg tlog -r 'outgoing("green")'
  abort: repository green does not exist
  [255]

  $ cd ..