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

     1

.\"                                      Hey, EMACS: -*- nroff -*-

     2

.\" First parameter, NAME, should be all caps

     3

.\" Second parameter, SECTION, should be 1-8, maybe w/ subsection

     4

.\" other parameters are allowed: see man(7), man(1)

     5

.TH CHG 1 "March 3, 2013"

     6

.\" Please adjust this date whenever revising the manpage.

     7

.\"

     8

.\" Some roff macros, for reference:

     9

.\" .nh        disable hyphenation

    10

.\" .hy        enable hyphenation

    11

.\" .ad l      left justify

    12

.\" .ad b      justify to both left and right margins

    13

.\" .nf        disable filling

    14

.\" .fi        enable filling

    15

.\" .br        insert line break

    16

.\" .sp <n>    insert n+1 empty lines

    17

.\" for manpage-specific macros, see man(7)

    18

.SH NAME

    19

chg \- a fast client for Mercurial command server

    20

.SH SYNOPSIS

    21

.B chg

    22

.IR command " [" options "] [" arguments "]..."

    23

.br

    24

.SH DESCRIPTION

    25

The

    26

.B chg

    27

command is the wrapper for

    28

.B hg

    29

command.

    30

It uses the Mercurial command server to reduce start-up overhead.

    31

.SH OPTIONS

    32

This program accepts the same command line syntax as the

    33

.B hg

    34

command. Additionally it accepts the following options.

    35

.TP

    36

.B \-\-kill\-chg\-daemon

    37

Terminate the background command servers.

    38

.SH SEE ALSO

    39

.BR hg (1)

    40

.SH AUTHOR

    41

Written by Yuya Nishihara <yuya@tcha.org>.