view tests/test-histedit-revspec.t @ 17970:0b03454abae7

ancestor: faster algorithm for difference of ancestor sets

One of the major reasons rebase is slow in large repositories is
the computation of the detach set: the set of ancestors of the
changesets to rebase not in the destination parent. This is currently
done via a revset that does two walks all the way to the root of
the DAG. Instead of doing that, to find ancestors of a set <revs>
not in another set <common> we walk up the tree in reverse revision
number order, maintaining sets of nodes visited from <revs>, <common>
or both.

For the common case where the sets are close both topologically and
in revision number (relative to repository size), this has been
found to speed up rebase by around 15-20%. When the nodes are farther
apart and the DAG is highly branching, it is harder to say which
would win.

Here's how long computing the detach set takes in a linear repository
with over 400000 changesets, rebasing near tip:

Rebasing across 4 changesets
Revset method: 2.2s
New algorithm: 0.00015s

Rebasing across 250 changesets
Revset method: 2.2s
New algorithm: 0.00069s

Rebasing across 10000 changesets
Revset method: 2.4s
New algorithm: 0.019s

This test requires parentrevspec support in revsets, so check for that
and skip the test if we're on an unusual hg that supports .t tests but
not parentrevspec.
  $ python -c 'from mercurial import revset ; revset.methods["parentpost"]' || exit 80

Enable extensions used by this test.
  $ cat >>$HGRCPATH <<EOF
  > [extensions]
  > graphlog=
  > histedit=
  > EOF

Repo setup.
  $ hg init foo
  $ cd foo
  $ echo alpha >> alpha
  $ hg addr
  adding alpha
  $ hg ci -m one
  $ echo alpha >> alpha
  $ hg ci -m two
  $ echo alpha >> alpha
  $ hg ci -m three
  $ echo alpha >> alpha
  $ hg ci -m four
  $ echo alpha >> alpha
  $ hg ci -m five

  $ hg log --style compact --graph
  @  4[tip]   08d98a8350f3   1970-01-01 00:00 +0000   test
  |    five
  |
  o  3   c8e68270e35a   1970-01-01 00:00 +0000   test
  |    four
  |
  o  2   eb57da33312f   1970-01-01 00:00 +0000   test
  |    three
  |
  o  1   579e40513370   1970-01-01 00:00 +0000   test
  |    two
  |
  o  0   6058cbb6cfd7   1970-01-01 00:00 +0000   test
       one
  

Run a dummy edit to make sure we get tip^^ correctly via revsingle.
  $ HGEDITOR=cat hg histedit "tip^^"
  pick eb57da33312f 2 three
  pick c8e68270e35a 3 four
  pick 08d98a8350f3 4 five
  
  # Edit history between eb57da33312f and 08d98a8350f3
  #
  # Commands:
  #  p, pick = use commit
  #  e, edit = use commit, but stop for amending
  #  f, fold = use commit, but fold into previous commit (combines N and N-1)
  #  d, drop = remove commit from history
  #  m, mess = edit message without changing commit content
  #
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

Run on a revision not ancestors of the current working directory.

  $ hg up 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg histedit -r 4
  nothing to edit
  [1]