view tests/test-merge-force.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

  $ hg init

  $ echo a > a
  $ hg ci -qAm 'add a'

  $ echo b > b
  $ hg ci -qAm 'add b'

  $ hg up -qC 0
  $ hg rm a
  $ hg ci -m 'rm a'
  created new head

  $ hg up -qC 1
  $ rm a

Local deleted a file, remote removed

Should fail, since there are deleted files:

  $ hg merge
  abort: outstanding uncommitted changes
  (use 'hg status' to list changes)
  [255]

Should succeed with --force:

  $ hg -v merge --force
  resolving manifests
  removing a
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

Should show 'a' as removed:

  $ hg status
  R a

  $ hg ci -m merge

Should not show 'a':

  $ hg manifest
  b