view mercurial/helptext/extensions.txt @ 45871:a985c4fb23ca

transaction: change list of journal entries into a dictionary

The transaction object used to keep a mapping table of path names to
journal entries and a list of journal entries consisting of path and
file offset to truncate on rollback. The offsets are used in three
cases. repair.strip and rollback process all of them in one go, but they
care about the order. For them, it is perfectly reasonable to read the
journal back from disk as both operations already involve at least one
system call per journal entry. The other consumer is the revlog logic
for moving from inline to external data storage. It doesn't care about
the order of the journal and just needs to original offset stored.
Further optimisations are possible here to move the in-memory journal to
a set(), but without memoisation of the original revlog size this could
turn it into O(n^2) behavior in worst case when many revlogs need to
migrated.

Differential Revision: https://phab.mercurial-scm.org/D9277

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 = !