view tests/test-rename-merge1.t @ 23785:cb99bacb9b4e

branchcache: introduce revbranchcache for caching of revision branch names

It is expensive to retrieve the branch name of a revision. Very expensive when
creating a changectx and calling .branch() every time - slightly less when
using changelog.branchinfo().

Now, to speed things up, provide a way to cache the results on disk in an
efficient format. Each branchname is assigned a number, and for each revision
we store the number of the corresponding branch name. The branch names are
stored in a dedicated file which is strictly append only.

Branch names are usually reused across several revisions, and the total list of
branch names will thus be so small that it is feasible to read the whole set of
names before using the cache. It will however do that it might be more
efficient to use the changelog for retrieving the branch info for a single
revision.

The revision entries are stored in another file. This file is usually append
only, but if the repository has been modified, the file will be truncated and
the relevant parts rewritten on demand.

The entries for each revision are 8 bytes each, and the whole revision file
will thus be 1/8 of 00changelog.i.

Each revision entry contains the first 4 bytes of the corresponding node hash.
This is used as a check sum that always is verified before the entry is used.
That check is relatively expensive but it makes sure history modification is
detected and handled correctly. It will also detect and handle most revision
file corruptions.

This is just a cache. A new format can always be introduced if other
requirements or ideas make that seem like a good idea. Rebuilding the cache is
not really more expensive than it was to run for example 'hg log -b branchname'
before this cache was introduced.

This new method is still unused but promise to make some operations several
times faster once it actually is used.

Abandoning Python 2.4 would make it possible to implement this more efficiently
by using struct classes and pack_into. The Python code could probably also be
micro optimized or it could be implemented very efficiently in C where it would
be easy to control the data access.

  $ hg init

  $ echo "[merge]" >> .hg/hgrc
  $ echo "followcopies = 1" >> .hg/hgrc

  $ echo foo > a
  $ echo foo > a2
  $ hg add a a2
  $ hg ci -m "start"

  $ hg mv a b
  $ hg mv a2 b2
  $ hg ci -m "rename"

  $ hg co 0
  2 files updated, 0 files merged, 2 files removed, 0 files unresolved

  $ echo blahblah > a
  $ echo blahblah > a2
  $ hg mv a2 c2
  $ hg ci -m "modify"
  created new head

  $ hg merge -y --debug
    searching for copies back to rev 1
    unmatched files in local:
     c2
    unmatched files in other:
     b
     b2
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' *
     src: 'a2' -> dst: 'b2' !
     src: 'a2' -> dst: 'c2' !
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: af1939970a1c, local: 044f8520aeeb+, remote: 85c198ef2f6c
   preserving a for resolve of b
  removing a
   b2: remote created -> g
  getting b2
  updating: b2 1/2 files (50.00%)
   b: remote moved from a -> m
  updating: b 2/2 files (100.00%)
  picked tool 'internal:merge' for b (binary False symlink False)
  merging a and b to b
  my b@044f8520aeeb+ other b@85c198ef2f6c ancestor a@af1939970a1c
   premerge successful
  note: possible conflict - a2 was renamed multiple times to:
   c2
   b2
  1 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg status -AC
  M b
    a
  M b2
  R a
  C c2

  $ cat b
  blahblah

  $ hg ci -m "merge"

  $ hg debugindex b
     rev    offset  length  ..... linkrev nodeid       p1           p2 (re)
       0         0      67  .....       1 57eacc201a7f 000000000000 000000000000 (re)
       1        67      72  .....       3 4727ba907962 000000000000 57eacc201a7f (re)

  $ hg debugrename b
  b renamed from a:dd03b83622e78778b403775d0d074b9ac7387a66

This used to trigger a "divergent renames" warning, despite no renames

  $ hg cp b b3
  $ hg cp b b4
  $ hg ci -A -m 'copy b twice'
  $ hg up eb92d88a9712
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg up
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg rm b3 b4
  $ hg ci -m 'clean up a bit of our mess'

We'd rather not warn on divergent renames done in the same changeset (issue2113)

  $ hg cp b b3
  $ hg mv b b4
  $ hg ci -A -m 'divergent renames in same changeset'
  $ hg up c761c6948de0
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg up
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved

Check for issue2642

  $ hg init t
  $ cd t

  $ echo c0 > f1
  $ hg ci -Aqm0

  $ hg up null -q
  $ echo c1 > f1 # backport
  $ hg ci -Aqm1
  $ hg mv f1 f2
  $ hg ci -qm2

  $ hg up 0 -q
  $ hg merge 1 -q --tool internal:local
  $ hg ci -qm3

  $ hg merge 2
  merging f1 and f2 to f2
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat f2
  c0

  $ cd ..

Check for issue2089

  $ hg init repo2089
  $ cd repo2089

  $ echo c0 > f1
  $ hg ci -Aqm0

  $ hg up null -q
  $ echo c1 > f1
  $ hg ci -Aqm1

  $ hg up 0 -q
  $ hg merge 1 -q --tool internal:local
  $ echo c2 > f1
  $ hg ci -qm2

  $ hg up 1 -q
  $ hg mv f1 f2
  $ hg ci -Aqm3

  $ hg up 2 -q
  $ hg merge 3
  merging f1 and f2 to f2
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat f2
  c2

  $ cd ..

Check for issue3074

  $ hg init repo3074
  $ cd repo3074
  $ echo foo > file
  $ hg add file
  $ hg commit -m "added file"
  $ hg mv file newfile
  $ hg commit -m "renamed file"
  $ hg update 0
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg rm file
  $ hg commit -m "deleted file"
  created new head
  $ hg merge --debug
    searching for copies back to rev 1
    unmatched files in other:
     newfile
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'file' -> dst: 'newfile' %
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 19d7f95df299, local: 0084274f6b67+, remote: 5d32493049f0
   newfile: remote created -> g
  getting newfile
  updating: newfile 1/1 files (100.00%)
  note: possible conflict - file was deleted and renamed to:
   newfile
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg status
  M newfile
  $ cd ..