bisect: avoid copying ancestor list for non-merge commits
During a bisection, hg needs to compute a list of all ancestors for every
candidate commit. This is accomplished via a bottom-up traversal of the set of
candidates, during which each revision's ancestor list is populated using the
ancestor list of its parent(s). Previously, this involved copying the entire
list, which could be very long in if the bisection range was large.
To help improve this, we can observe that each candidate commit is visited
exactly once, at which point its ancestor list is copied into its children's
lists and then dropped. In the case of non-merge commits, a commit's ancestor
list consists exactly of its parent's list plus itself. This means that we can
trivially reuse the parent's existing list for one of its non-merge children,
which avoids copying entirely if that commit is the parent's only child. This
makes bisections over linear ranges of commits much faster.
During some informal testing in the large publicly-available `mozilla-central`
repository, this noticeably sped up bisections over large ranges of history:
Setup:
$ cd mozilla-central
$ hg bisect --reset
$ hg bisect --good 0
$ hg log -r tip -T '{rev}\n'
628417
Test:
$ time hg bisect --bad tip --noupdate
Before:
real 3m35.927s
user 3m35.553s
sys 0m0.319s
After:
real 1m41.142s
user 1m40.810s
sys 0m0.285s
bundle w/o type option
$ hg init t1
$ hg init t2
$ cd t1
$ echo blablablablabla > file.txt
$ hg ci -Ama
adding file.txt
$ hg log | grep summary
summary: a
$ hg bundle ../b1 ../t2
searching for changes
1 changesets found
$ cd ../t2
$ hg unbundle ../b1
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets c35a0f9217e6 (1 drafts)
(run 'hg update' to get a working copy)
$ hg up
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg log | grep summary
summary: a
$ cd ..
Unknown compression type is rejected
$ hg init t3
$ cd t3
$ hg -q unbundle ../b1
$ hg bundle -a -t unknown out.hg
abort: unknown is not a recognized bundle specification
(see 'hg help bundlespec' for supported values for --type)
[10]
$ hg bundle -a -t unknown-v2 out.hg
abort: unknown compression is not supported
(see 'hg help bundlespec' for supported values for --type)
[10]
$ cd ..
test bundle types
$ testbundle() {
> echo % test bundle type $1
> hg init t$1
> cd t1
> hg bundle -t $1 ../b$1 ../t$1
> f -q -B6 -D ../b$1; echo
> cd ../t$1
> hg debugbundle ../b$1
> hg debugbundle --spec ../b$1
> echo
> cd ..
> }
$ for t in "None" "bzip2" "gzip" "none-v2" "v2" "v1" "gzip-v1"; do
> testbundle $t
> done
% test bundle type None
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: {}
changegroup -- {nbchanges: 1, version: 02} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
cache:rev-branch-cache -- {} (mandatory: False)
none-v2
% test bundle type bzip2
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 1, version: 02} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
cache:rev-branch-cache -- {} (mandatory: False)
bzip2-v2
% test bundle type gzip
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: {Compression: GZ}
changegroup -- {nbchanges: 1, version: 02} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
cache:rev-branch-cache -- {} (mandatory: False)
gzip-v2
% test bundle type none-v2
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: {}
changegroup -- {nbchanges: 1, version: 02} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
cache:rev-branch-cache -- {} (mandatory: False)
none-v2
% test bundle type v2
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 1, version: 02} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
cache:rev-branch-cache -- {} (mandatory: False)
bzip2-v2
% test bundle type v1
searching for changes
1 changesets found
HG10BZ
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
bzip2-v1
% test bundle type gzip-v1
searching for changes
1 changesets found
HG10GZ
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
gzip-v1
Compression level can be adjusted for bundle2 bundles
$ hg init test-complevel
$ cd test-complevel
$ cat > file0 << EOF
> this is a file
> with some text
> and some more text
> and other content
> EOF
$ cat > file1 << EOF
> this is another file
> with some other content
> and repeated, repeated, repeated, repeated content
> EOF
$ hg -q commit -A -m initial
$ hg bundle -a -t gzip-v2 gzip-v2.hg
1 changesets found
$ f --size gzip-v2.hg
gzip-v2.hg: size=468
$ hg --config experimental.bundlecomplevel=1 bundle -a -t gzip-v2 gzip-v2-level1.hg
1 changesets found
$ f --size gzip-v2-level1.hg
gzip-v2-level1.hg: size=475
$ hg --config experimental.bundlecomplevel.gzip=1 --config experimental.bundlelevel=9 bundle -a -t gzip-v2 gzip-v2-level1.hg
1 changesets found
$ f --size gzip-v2-level1.hg
gzip-v2-level1.hg: size=475
$ cd ..
#if zstd
$ for t in "zstd" "zstd-v2"; do
> testbundle $t
> done
% test bundle type zstd
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: {Compression: ZS}
changegroup -- {nbchanges: 1, version: 02} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
cache:rev-branch-cache -- {} (mandatory: False)
zstd-v2
% test bundle type zstd-v2
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: {Compression: ZS}
changegroup -- {nbchanges: 1, version: 02} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
cache:rev-branch-cache -- {} (mandatory: False)
zstd-v2
Explicit request for zstd on non-generaldelta repos
$ hg --config format.usegeneraldelta=false init nogd
$ hg -q -R nogd pull t1
$ hg -R nogd bundle -a -t zstd nogd-zstd
1 changesets found
zstd-v1 always fails
$ hg -R tzstd bundle -a -t zstd-v1 zstd-v1
abort: compression engine zstd is not supported on v1 bundles
(see 'hg help bundlespec' for supported values for --type)
[10]
zstd supports threading
$ hg init test-compthreads
$ cd test-compthreads
$ hg debugbuilddag +3
$ hg --config experimental.bundlecompthreads=1 bundle -a -t zstd-v2 zstd-v2-threaded.hg
3 changesets found
$ cd ..
#else
zstd is a valid engine but isn't available
$ hg -R t1 bundle -a -t zstd irrelevant.hg
abort: compression engine zstd could not be loaded
[255]
#endif
test garbage file
$ echo garbage > bgarbage
$ hg init tgarbage
$ cd tgarbage
$ hg pull ../bgarbage
pulling from ../bgarbage
abort: ../bgarbage: not a Mercurial bundle
[255]
$ cd ..
test invalid bundle type
$ cd t1
$ hg bundle -a -t garbage ../bgarbage
abort: garbage is not a recognized bundle specification
(see 'hg help bundlespec' for supported values for --type)
[10]
$ cd ..
Test controlling the changegroup version
$ hg -R t1 bundle --config experimental.changegroup3=yes -a -t v2 ./v2-cg-default.hg
1 changesets found
$ hg debugbundle ./v2-cg-default.hg --part-type changegroup
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 1, version: 02} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
$ hg debugbundle ./v2-cg-default.hg --spec
bzip2-v2
$ hg -R t1 bundle --config experimental.changegroup3=yes -a -t 'v2;cg.version=02' ./v2-cg-02.hg
1 changesets found
$ hg debugbundle ./v2-cg-02.hg --part-type changegroup
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 1, version: 02} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
$ hg debugbundle ./v2-cg-02.hg --spec
bzip2-v2
$ hg -R t1 bundle --config experimental.changegroup3=yes -a -t 'v2;cg.version=03' ./v2-cg-03.hg
1 changesets found
$ hg debugbundle ./v2-cg-03.hg --part-type changegroup
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 1, version: 03} (mandatory: True)
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
$ hg debugbundle ./v2-cg-03.hg --spec
bzip2-v2;cg.version=03