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changegroup: store old heads as a set...
changegroup: store old heads as a set Previously, the "oldheads" variable was a list. On a repository at Mozilla with 46,492 heads, profiling revealed that list membership testing was dominating execution time of applying small changegroups. This patch converts the list of old heads to a set. This makes membership testing significantly faster. On the aforementioned repository with 46,492 heads: $ hg unbundle <file with 1 changeset> before: 18.535s wall after: 1.303s Consumers of this variable only check for truthiness (`if oldheads`), length (`len(oldheads)`), and (most importantly) item membership (`h not in oldheads` - which occurs twice). So, the change to a set should be safe and suitable for stable. The practical effect of this change is that changegroup application and related operations (like `hg push`) no longer exhibit an O(n^2) CPU explosion as the number of heads grows.

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r19296:da16d21c stable
r31587:ed5b2587 4.1.2 stable
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extensions.txt
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Mercurial has the ability to add new features through the use of
extensions. Extensions may add new commands, add options to
existing commands, change the default behavior of commands, or
implement hooks.
To enable the "foo" extension, either shipped with Mercurial or in the
Python search path, create an entry for it in your configuration file,
like this::
[extensions]
foo =
You may also specify the full path to an extension::
[extensions]
myfeature = ~/.hgext/myfeature.py
See :hg:`help config` for more information on configuration files.
Extensions are not loaded by default for a variety of reasons:
they can increase startup overhead; they may be meant for advanced
usage only; they may provide potentially dangerous abilities (such
as letting you destroy or modify history); they might not be ready
for prime time; or they may alter some usual behaviors of stock
Mercurial. It is thus up to the user to activate extensions as
needed.
To explicitly disable an extension enabled in a configuration file of
broader scope, prepend its path with !::
[extensions]
# disabling extension bar residing in /path/to/extension/bar.py
bar = !/path/to/extension/bar.py
# ditto, but no path was supplied for extension baz
baz = !