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rebase: use matcher to optimize manifestmerge...
rebase: use matcher to optimize manifestmerge The old merge code would call manifestmerge and calculate the complete diff between the source to the destination. In many cases, like rebase, the vast majority of differences between the source and destination are irrelevant because they are differences between the destination and the common ancestor only, and therefore don't affect the merge. Since most actions are 'keep', all the effort to compute them is wasted. Instead, let's compute the difference between the source and the common ancestor and only perform the diff of those files against the merge destination. When using treemanifest, this lets us avoid loading almost the entire tree when rebasing from a very old ancestor. This speeds up rebase of an old stack of 27 commits by 20x. In mozilla-central, without treemanifest, when rebasing a commit from default~100000 to default, this speeds up the manifestmerge step from 2.6s to 1.2s. However, the additional diff adds an overhead to all manifestmerge calls, especially for flat manifests. When rebasing a commit from default~1 to default it appears to add 100ms in mozilla-central. While we could put this optimization behind a flag, I think the fact that it makes merge O(number of changes being applied) instead of O(number of changes between X and Y) justifies it.

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test-issue672.t
99 lines | 2.9 KiB | text/troff | Tads3Lexer
https://bz.mercurial-scm.org/672
# 0-2-4
# \ \ \
# 1-3-5
#
# rename in #1, content change in #4.
$ hg init
$ touch 1
$ touch 2
$ hg commit -Am init # 0
adding 1
adding 2
$ hg rename 1 1a
$ hg commit -m rename # 1
$ hg co -C 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo unrelated >> 2
$ hg ci -m unrelated1 # 2
created new head
$ hg merge --debug 1
searching for copies back to rev 1
unmatched files in other:
1a
all copies found (* = to merge, ! = divergent, % = renamed and deleted):
src: '1' -> dst: '1a'
checking for directory renames
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 81f4b099af3d, local: c64f439569a9+, remote: c12dcd37c90a
1: other deleted -> r
removing 1
1a: remote created -> g
getting 1a
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -m merge1 # 3
$ hg co -C 2
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo hello >> 1
$ hg ci -m unrelated2 # 4
created new head
$ hg co -C 3
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg merge -y --debug 4
searching for copies back to rev 1
unmatched files in local:
1a
all copies found (* = to merge, ! = divergent, % = renamed and deleted):
src: '1' -> dst: '1a' *
checking for directory renames
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: c64f439569a9, local: e327dca35ac8+, remote: 746e9549ea96
preserving 1a for resolve of 1a
starting 4 threads for background file closing (?)
1a: local copied/moved from 1 -> m (premerge)
picked tool ':merge' for 1a (binary False symlink False changedelete False)
merging 1a and 1 to 1a
my 1a@e327dca35ac8+ other 1@746e9549ea96 ancestor 1@c64f439569a9
premerge successful
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg co -C 4
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg merge -y --debug 3
searching for copies back to rev 1
unmatched files in other:
1a
all copies found (* = to merge, ! = divergent, % = renamed and deleted):
src: '1' -> dst: '1a' *
checking for directory renames
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: c64f439569a9, local: 746e9549ea96+, remote: e327dca35ac8
preserving 1 for resolve of 1a
removing 1
starting 4 threads for background file closing (?)
1a: remote moved from 1 -> m (premerge)
picked tool ':merge' for 1a (binary False symlink False changedelete False)
merging 1 and 1a to 1a
my 1a@746e9549ea96+ other 1a@e327dca35ac8 ancestor 1@c64f439569a9
premerge successful
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)