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

#!/usr/bin/env bash

     2

# A simple script for opening merge conflicts in the editor.

     3

# Use the following Mercurial settings to enable it.

     4

#

     5

# [ui]

     6

# merge = editmerge

     7

#

     8

# [merge-tools]

     9

# editmerge.args=$output

    10

# editmerge.check=changed

    11

# editmerge.premerge=keep

    12

    13

FILE="$1"

    14

    15

getlines() {

    16

  grep -n "^<<<<<<" "$FILE" | cut -f1 -d:

    17

}

    18

    19

# editor preference loosely based on https://mercurial-scm.org/wiki/editor

    20

# hg showconfig is at the bottom though, since it's slow to run (0.15 seconds)

    21

ED="$HGEDITOR"

    22

if [ "$ED" = "" ] ; then

    23

  ED="$VISUAL"

    24

fi

    25

if [ "$ED" = "" ] ; then

    26

  ED="$EDITOR"

    27

fi

    28

if [ "$ED" = "" ] ; then

    29

  ED="$(hg showconfig ui.editor)"

    30

fi

    31

if [ "$ED" = "" ] ; then

    32

  echo "merge failed - unable to find editor"

    33

  exit 1

    34

fi

    35

    36

if [ "$ED" = "emacs" ] || [ "$ED" = "nano" ] || [ "$ED" = "vim" ] ; then

    37

  FIRSTLINE="$(getlines | head -n 1)"

    38

  PREVIOUSLINE=""

    39

    40

  # open the editor to the first conflict until there are no more

    41

  # or the user stops editing the file

    42

  while [ ! "$FIRSTLINE" = "" ] && [ ! "$FIRSTLINE" = "$PREVIOUSLINE" ] ; do

    43

    $ED "+$FIRSTLINE" "$FILE"

    44

    PREVIOUSLINE="$FIRSTLINE"

    45

    FIRSTLINE="$(getlines | head -n 1)"

    46

  done

    47

else

    48

  $ED "$FILE"

    49

fi

    50

    51

# get the line numbers of the remaining conflicts

    52

CONFLICTS="$(getlines | sed ':a;N;$!ba;s/\n/, /g')"

    53

if [ ! "$CONFLICTS" = "" ] ; then

    54

  echo "merge failed - resolve the conflicts (line $CONFLICTS) then use 'hg resolve --mark'"

    55

  exit 1

    56

fi

    57

    58

exit 0