mercurial/help/extensions.txt

filemerge: add config knob to check capabilities of internal merge tools

For historical reason, Mercurial assumes capabilities of internal
merge tools as below while examining rules to decide merge tool,
regardless of actual capabilities of them.

    =============== ====== ========
    specified via   binary symlinks
    =============== ====== ========
    --tool          o      o
    HGMERGE         o      o
    merge-patterns  o (*)  x (*)
    ui.merge        x (*)  x (*)
    =============== ====== ========

This causes:

  - unintentional internal merge tool is chosen for binary files via
    merge-patterns section of configuration file

  - explicit configuration of internal merge tool for symlinks is
    ignored unintentionally

But on the other hand, simple "check capability strictly" might break
backward compatibility (e.g. existing merge automations), because it
changes the result of merge tool selection.

Therefore, this patch adds config knob "merge.strict-capability-check"
to control whether capabilities of internal merge tools should be
checked strictly or not.

If this configuration is true, capabilities of internal merge tools
are checked strictly in (*) cases above.

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 = !