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

test sparse

     2

     3

  $ hg init myrepo

     4

  $ cd myrepo

     5

  $ cat >> $HGRCPATH <<EOF

     6

  > [extensions]

     7

  > sparse=

     8

  > purge=

     9

  > strip=

    10

  > rebase=

    11

  > EOF

    12

    13

  $ echo a > index.html

    14

  $ echo x > data.py

    15

  $ echo z > readme.txt

    16

  $ cat > base.sparse <<EOF

    17

  > [include]

    18

  > *.sparse

    19

  > EOF

    20

  $ hg ci -Aqm 'initial'

    21

  $ cat > webpage.sparse <<EOF

    22

  > %include base.sparse

    23

  > [include]

    24

  > *.html

    25

  > EOF

    26

  $ hg ci -Aqm 'initial'

    27

    28

Clear rules when there are includes

    29

    30

  $ hg debugsparse --include *.py

    31

  $ ls -A

    32

  .hg

    33

  data.py

    34

  $ hg debugsparse --clear-rules

    35

  $ ls -A

    36

  .hg

    37

  base.sparse

    38

  data.py

    39

  index.html

    40

  readme.txt

    41

  webpage.sparse

    42

    43

Clear rules when there are excludes

    44

    45

  $ hg debugsparse -X base.sparse -X webpage.sparse

    46

  $ ls -A

    47

  .hg

    48

  data.py

    49

  index.html

    50

  readme.txt

    51

  $ hg debugsparse --clear-rules

    52

  $ ls -A

    53

  .hg

    54

  base.sparse

    55

  data.py

    56

  index.html

    57

  readme.txt

    58

  webpage.sparse

    59

    60

Clearing rules should not alter profiles

    61

    62

  $ hg debugsparse --enable-profile webpage.sparse

    63

  $ ls -A

    64

  .hg

    65

  base.sparse

    66

  index.html

    67

  webpage.sparse

    68

  $ hg debugsparse --include *.py

    69

  $ ls -A

    70

  .hg

    71

  base.sparse

    72

  data.py

    73

  index.html

    74

  webpage.sparse

    75

  $ hg debugsparse --clear-rules

    76

  $ ls -A

    77

  .hg

    78

  base.sparse

    79

  index.html

    80

  webpage.sparse