repoview: cache filtered changelog
Creating a new changelog object for each access is costly and prevents efficient
caching changelog side. This introduced a x5 performance regression in log
because chunk read from disk were never reused. We were jumping from about 100
disk read to about 20 000.
This changeset introduce a simple cache mechanism that help the last changelog
object created by a repoview. The changelog is reused until the changelog or the
filtering changes.
The cache invalidation is much more complicated than it should be. But MQ test
show a strange cache desync. I was unable to track down the source of this
desync in descent time so I'm not sure if the issue is in MQ or core. However
given the proximity to the 2.5 freeze, I'm choosing the inelegant but safe route
that makes the cache mechanism safer.
rebase: do not invent successor to skipped changeset
When rebase results in an empty a changeset it is "skipped" and no related
changeset is created at all. When we added obsolescence support to rebase (in
fc2a6114f0a0) it seemed a good idea to use its parent successor as the
successors for such dropped changesets. (see old version of the altered test).
This option was chosen because it seems a good way to hint about were the
dropped changeset "intended" to be. Such hint would have been used by automatic
evolution mechanism to rebase potential unstable children.
However, field testing of this version are not conclusive. It very often leads
to the creation of (totally unfounded) evolution divergence. This changeset
changes this behavior and mark skipped changesets as pruned (obsolete without
successors). This prevents the issue and seems semantically better probably a
win for obsolescence reading tool.
See example bellow for details:
User Babar has five changesets of interest:
- O, its current base of development.
- U, the new upstream
- A and C, some development changesets
- B another development changeset independent from A
O - A - B - C
\
U
Babar decides that B is more critical than the A and C and rebase it first
$ hg rebase --rev B --dest U
B is now obsolete (in lower case bellow). Rebase result, B', is its
successors.(note, C is unstable)
O - A - b - C
\
U - B'
Babar is now done with B', and want to rebase the rest of its history:
$ hg rebase --source A --dest B'
hg rebase process A, B and C. B is skipped as all its changes are already contained
in B'.
O - U - B' - A' - C'
Babar have the expected result graph wise, obsolescence marker are as follow:
B -> B' (from first rebase)
A -> A' (from second rebase)
C -> C' (from second rebase)
B -> ?? (from second rebase)
Before this changeset, the last marker is `B -> A'`. This cause two issues:
- This is semantically wrong. B have nothing to do with A'
- B has now two successors sets: (B',) and (A',). We detect a divergent
rewriting. The B' and A' are reported as "divergent" to Babar, confusion
ensues. In addition such divergent situation (divergent changeset are children
to each other) is tricky to solve.
With this changeset the last marker is `B -> ΓΈ`:
- This is semantically better.
- B has a single successors set (B',)
This scenario is added to the tests suite.
repoview: protect `base` computation from weird phase root
If for some reason the phase roots contains nullid, the set of filtered revs
will contains -1. That confuse Mercurial a lot. In particular this corrupt the
branchcache.
Standard code path does not result in nullid phase root. It can only result from
altered `.hg/store/phaseroots` or buggy extension. However better safe than
sorry.
posix: don't compare atime when determining if a file has changed
A file's atime might change even if the file itself doesn't change. This might
cause us to invalidate caches more often than necessary.
Before this change, hg add often resulted in the dirstate being parsed twice
on systems that track atime. After this change, it is only parsed once. For a
repository with over 180,000 files, this speeds up hg add from 1.2 seconds to
1.0.
histedit: proper phase conservation (
issue3724)
Before this changeset, histedit created all new changesets according
phases.new-commit option without any regards for the phases of the original
changesets.
This changeset fix that using the phase of rewritten changeset to decide the
phase of the resulting changeset. In case of reordering or folding, we keep
secret item secret as it seems the safer path.
temporary commit creation are not affected. They are head only and stripped at
the end of the histedit.
As for the resolution of
issue3681 (obsolescence cycle prevention), we do not
handle changesets created by edit command.