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
$ hg init a
$ cd a
$ cp "$TESTDIR/binfile.bin" .
$ hg add binfile.bin
$ hg ci -m 'add binfile.bin'
$ echo >> binfile.bin
$ hg ci -m 'change binfile.bin'
$ hg revert -r 0 binfile.bin
$ hg ci -m 'revert binfile.bin'
$ hg cp binfile.bin nonbinfile
$ echo text > nonbinfile
$ hg ci -m 'make non-binary copy of binary file'
$ hg diff --nodates -r 0 -r 1
diff -r 48b371597640 -r acea2ab458c8 binfile.bin
Binary file binfile.bin has changed
$ hg diff --nodates -r 0 -r 2
$ hg diff --git -r 0 -r 1
diff --git a/binfile.bin b/binfile.bin
index 37ba3d1c6f17137d9c5f5776fa040caf5fe73ff9..58dc31a9e2f40f74ff3b45903f7d620b8e5b7356
GIT binary patch
literal 594
zc$@)J0<HatP)<h;3K|Lk000e1NJLTq000mG000mO0ssI2kdbIM00009a7bBm000XU
z000XU0RWnu7ytkO2XskIMF-Uh9TW;VpMjwv0005-Nkl<ZD9@FWPs=e;7{<>W$NUkd
zX$nnYLt$-$V!?uy+1V%`z&Eh=ah|duER<4|QWhju3gb^nF*8iYobxWG-qqXl=2~5M
z*IoDB)sG^CfNuoBmqLTVU^<;@nwHP!1wrWd`{(mHo6VNXWtyh{alzqmsH*yYzpvLT
zLdY<T=ks|woh-`&01!ej#(xbV1f|pI*=%;d-%F*E*X#ZH`4I%6SS+$EJDE&ct=8po
ziN#{?_j|kD%Cd|oiqds`xm@;oJ-^?NG3Gdqrs?5u*zI;{nogxsx~^|Fn^Y?Gdc6<;
zfMJ+iF1J`LMx&A2?dEwNW8ClebzPTbIh{@$hS6*`kH@1d%Lo7fA#}N1)oN7`gm$~V
z+wDx#)OFqMcE{s!JN0-xhG8ItAjVkJwEcb`3WWlJfU2r?;Pd%dmR+q@mSri5q9_W-
zaR2~ECX?B2w+zELozC0s*6Z~|QG^f{3I#<`?)Q7U-JZ|q5W;9Q8i_=pBuSzunx=U;
z9C)5jBoYw9^?EHyQl(M}1OlQcCX>lXB*ODN003Z&P17_@)3Pi=i0wb04<W?v-u}7K
zXmmQA+wDgE!qR9o8jr`%=ab_&uh(l?R=r;Tjiqon91I2-hIu?57~@*4h7h9uORK#=
gQItJW-{SoTm)8|5##k|m00000NkvXXu0mjf3JwksH2?qr
$ hg diff --git -r 0 -r 2
$ hg diff --config diff.nobinary=True --git -r 0 -r 1
diff --git a/binfile.bin b/binfile.bin
Binary file binfile.bin has changed
$ HGPLAIN=1 hg diff --config diff.nobinary=True --git -r 0 -r 1
diff --git a/binfile.bin b/binfile.bin
index 37ba3d1c6f17137d9c5f5776fa040caf5fe73ff9..58dc31a9e2f40f74ff3b45903f7d620b8e5b7356
GIT binary patch
literal 594
zc$@)J0<HatP)<h;3K|Lk000e1NJLTq000mG000mO0ssI2kdbIM00009a7bBm000XU
z000XU0RWnu7ytkO2XskIMF-Uh9TW;VpMjwv0005-Nkl<ZD9@FWPs=e;7{<>W$NUkd
zX$nnYLt$-$V!?uy+1V%`z&Eh=ah|duER<4|QWhju3gb^nF*8iYobxWG-qqXl=2~5M
z*IoDB)sG^CfNuoBmqLTVU^<;@nwHP!1wrWd`{(mHo6VNXWtyh{alzqmsH*yYzpvLT
zLdY<T=ks|woh-`&01!ej#(xbV1f|pI*=%;d-%F*E*X#ZH`4I%6SS+$EJDE&ct=8po
ziN#{?_j|kD%Cd|oiqds`xm@;oJ-^?NG3Gdqrs?5u*zI;{nogxsx~^|Fn^Y?Gdc6<;
zfMJ+iF1J`LMx&A2?dEwNW8ClebzPTbIh{@$hS6*`kH@1d%Lo7fA#}N1)oN7`gm$~V
z+wDx#)OFqMcE{s!JN0-xhG8ItAjVkJwEcb`3WWlJfU2r?;Pd%dmR+q@mSri5q9_W-
zaR2~ECX?B2w+zELozC0s*6Z~|QG^f{3I#<`?)Q7U-JZ|q5W;9Q8i_=pBuSzunx=U;
z9C)5jBoYw9^?EHyQl(M}1OlQcCX>lXB*ODN003Z&P17_@)3Pi=i0wb04<W?v-u}7K
zXmmQA+wDgE!qR9o8jr`%=ab_&uh(l?R=r;Tjiqon91I2-hIu?57~@*4h7h9uORK#=
gQItJW-{SoTm)8|5##k|m00000NkvXXu0mjf3JwksH2?qr
$ hg diff --git -r 2 -r 3
diff --git a/binfile.bin b/nonbinfile
copy from binfile.bin
copy to nonbinfile
index 37ba3d1c6f17137d9c5f5776fa040caf5fe73ff9..8e27be7d6154a1f68ea9160ef0e18691d20560dc
GIT binary patch
literal 5
Mc$_OqttjCF00uV!&;S4c
$ cd ..
Test text mode with extended git-style diff format
$ hg init b
$ cd b
$ cat > writebin.py <<EOF
> import sys
> path = sys.argv[1]
> open(path, 'wb').write(b'\x00\x01\x02\x03')
> EOF
$ "$PYTHON" writebin.py binfile.bin
$ hg add binfile.bin
$ hg ci -m 'add binfile.bin'
$ echo >> binfile.bin
$ hg ci -m 'change binfile.bin'
$ hg diff --git -a -r 0 -r 1
diff --git a/binfile.bin b/binfile.bin
--- a/binfile.bin
+++ b/binfile.bin
@@ -1,1 +1,1 @@
-\x00\x01\x02\x03 (esc)
\ No newline at end of file
+\x00\x01\x02\x03 (esc)
$ HGPLAIN=1 hg diff --git -a -r 0 -r 1
diff --git a/binfile.bin b/binfile.bin
--- a/binfile.bin
+++ b/binfile.bin
@@ -1,1 +1,1 @@
-\x00\x01\x02\x03 (esc)
\ No newline at end of file
+\x00\x01\x02\x03 (esc)
Test binary mode with extended git-style diff format
$ hg diff --no-binary -r 0 -r 1
diff -r fb45f71337ad -r 9ca112d1a3c1 binfile.bin
Binary file binfile.bin has changed
$ hg diff --git --no-binary -r 0 -r 1
diff --git a/binfile.bin b/binfile.bin
Binary file binfile.bin has changed
$ hg diff --git --binary -r 0 -r 1
diff --git a/binfile.bin b/binfile.bin
index eaf36c1daccfdf325514461cd1a2ffbc139b5464..ba71a782e93f3fb63a428383706065e3ec2828e9
GIT binary patch
literal 5
Mc${NkWMbw50018V5dZ)H
$ hg diff --git --binary --config diff.nobinary=True -r 0 -r 1
diff --git a/binfile.bin b/binfile.bin
index eaf36c1daccfdf325514461cd1a2ffbc139b5464..ba71a782e93f3fb63a428383706065e3ec2828e9
GIT binary patch
literal 5
Mc${NkWMbw50018V5dZ)H
$ hg diff --git --binary --text -r 0 -r 1
diff --git a/binfile.bin b/binfile.bin
--- a/binfile.bin
+++ b/binfile.bin
@@ -1,1 +1,1 @@
-\x00\x01\x02\x03 (esc)
\ No newline at end of file
+\x00\x01\x02\x03 (esc)
$ cd ..