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
# same user, same group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# same user, different group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, same group
not trusting file .hg/hgrc from untrusted user abc, group bar
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, same group, but we trust the group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, different group, but we trust the user
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, different group, but we trust the group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, different group, but we trust the user and the group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# we trust all users
# different user, different group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# we trust all groups
# different user, different group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# we trust all users and groups
# different user, different group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# we don't get confused by users and groups with the same name
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# list of user names
# different user, different group, but we trust the user
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# list of group names
# different user, different group, but we trust the group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# Can't figure out the name of the user running this process
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# prints debug warnings
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
ignoring untrusted configuration option paths.local = /another/path
global = /some/path
untrusted
. . global = /some/path
. ignoring untrusted configuration option paths.local = /another/path
. local = /another/path
# report_untrusted enabled without debug hides warnings
# different user, different group
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# report_untrusted enabled with debug shows warnings
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
ignoring untrusted configuration option paths.local = /another/path
global = /some/path
untrusted
. . global = /some/path
. ignoring untrusted configuration option paths.local = /another/path
. local = /another/path
# ui.readconfig sections
quux
# read trusted, untrusted, new ui, trusted
not trusting file foobar from untrusted user abc, group def
trusted:
ignoring untrusted configuration option foobar.baz = quux
None
untrusted:
quux
# error handling
# file doesn't exist
# same user, same group
# different user, different group
# parse error
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
ignored .hg/hgrc:1: foo
# same user, same group
config error at .hg/hgrc:1: foo
# access typed information
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
# suboptions, trusted and untrusted
(None, []) ('main', [('one', 'one'), ('two', 'two')])
# path, trusted and untrusted
None .hg/monty/python
# bool, trusted and untrusted
False True
# int, trusted and untrusted
0 42
# bytes, trusted and untrusted
0 84934656
# list, trusted and untrusted
[] ['spam', 'ham', 'eggs']