help: add additional information in the merge-tools section of config help

The merge tool configuration in general has always been a confusing topic for
user. We add mention of:
- possible pre-existing configuration,
- way to look at it,
- the more detailed help topic about how merge-tools configuration works.

This should help users find they way.

mercurial/help/config.txt

@@ -1,1547 +1,1549
 The Mercurial system uses a set of configuration files to control
 aspects of its behavior.
 
 The configuration files use a simple ini-file format. A configuration
 file consists of sections, led by a ``[section]`` header and followed
 by ``name = value`` entries::
 
   [ui]
   username = Firstname Lastname <[e-mail]>
   verbose = True
 
 The above entries will be referred to as ``ui.username`` and
 ``ui.verbose``, respectively. See the Syntax section below.
 
 Files
 =====
 
 Mercurial reads configuration data from several files, if they exist.
 These files do not exist by default and you will have to create the
 appropriate configuration files yourself: global configuration like
 the username setting is typically put into
 ``%USERPROFILE%\mercurial.ini`` or ``$HOME/.hgrc`` and local
 configuration is put into the per-repository ``<repo>/.hg/hgrc`` file.
 
 The names of these files depend on the system on which Mercurial is
 installed. ``*.rc`` files from a single directory are read in
 alphabetical order, later ones overriding earlier ones. Where multiple
 paths are given below, settings from earlier paths override later
 ones.
 
 | (All) ``<repo>/.hg/hgrc``
 
     Per-repository configuration options that only apply in a
     particular repository. This file is not version-controlled, and
     will not get transferred during a "clone" operation. Options in
     this file override options in all other configuration files. On
     Plan 9 and Unix, most of this file will be ignored if it doesn't
     belong to a trusted user or to a trusted group. See the documentation
     for the ``[trusted]`` section below for more details.
 
 | (Plan 9) ``$home/lib/hgrc``
 | (Unix) ``$HOME/.hgrc``
 | (Windows) ``%USERPROFILE%\.hgrc``
 | (Windows) ``%USERPROFILE%\Mercurial.ini``
 | (Windows) ``%HOME%\.hgrc``
 | (Windows) ``%HOME%\Mercurial.ini``
 
     Per-user configuration file(s), for the user running Mercurial. On
     Windows 9x, ``%HOME%`` is replaced by ``%APPDATA%``. Options in these
     files apply to all Mercurial commands executed by this user in any
     directory. Options in these files override per-system and per-installation
     options.
 
 | (Plan 9) ``/lib/mercurial/hgrc``
 | (Plan 9) ``/lib/mercurial/hgrc.d/*.rc``
 | (Unix) ``/etc/mercurial/hgrc``
 | (Unix) ``/etc/mercurial/hgrc.d/*.rc``
 
     Per-system configuration files, for the system on which Mercurial
     is running. Options in these files apply to all Mercurial commands
     executed by any user in any directory. Options in these files
     override per-installation options.
 
 | (Plan 9) ``<install-root>/lib/mercurial/hgrc``
 | (Plan 9) ``<install-root>/lib/mercurial/hgrc.d/*.rc``
 | (Unix) ``<install-root>/etc/mercurial/hgrc``
 | (Unix) ``<install-root>/etc/mercurial/hgrc.d/*.rc``
 
     Per-installation configuration files, searched for in the
     directory where Mercurial is installed. ``<install-root>`` is the
     parent directory of the **hg** executable (or symlink) being run. For
     example, if installed in ``/shared/tools/bin/hg``, Mercurial will look
     in ``/shared/tools/etc/mercurial/hgrc``. Options in these files apply
     to all Mercurial commands executed by any user in any directory.
 
 | (Windows) ``<install-dir>\Mercurial.ini`` **or**
 | (Windows) ``<install-dir>\hgrc.d\*.rc`` **or**
 | (Windows) ``HKEY_LOCAL_MACHINE\SOFTWARE\Mercurial``
 
     Per-installation/system configuration files, for the system on
     which Mercurial is running. Options in these files apply to all
     Mercurial commands executed by any user in any directory. Registry
     keys contain PATH-like strings, every part of which must reference
     a ``Mercurial.ini`` file or be a directory where ``*.rc`` files will
     be read.  Mercurial checks each of these locations in the specified
     order until one or more configuration files are detected.
 
 .. note::
 
    The registry key ``HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Mercurial``
    is used when running 32-bit Python on 64-bit Windows.
 
 Syntax
 ======
 
 A configuration file consists of sections, led by a ``[section]`` header
 and followed by ``name = value`` entries (sometimes called
 ``configuration keys``)::
 
     [spam]
     eggs=ham
     green=
        eggs
 
 Each line contains one entry. If the lines that follow are indented,
 they are treated as continuations of that entry. Leading whitespace is
 removed from values. Empty lines are skipped. Lines beginning with
 ``#`` or ``;`` are ignored and may be used to provide comments.
 
 Configuration keys can be set multiple times, in which case Mercurial
 will use the value that was configured last. As an example::
 
     [spam]
     eggs=large
     ham=serrano
     eggs=small
 
 This would set the configuration key named ``eggs`` to ``small``.
 
 It is also possible to define a section multiple times. A section can
 be redefined on the same and/or on different configuration files. For
 example::
 
     [foo]
     eggs=large
     ham=serrano
     eggs=small
 
     [bar]
     eggs=ham
     green=
        eggs
 
     [foo]
     ham=prosciutto
     eggs=medium
     bread=toasted
 
 This would set the ``eggs``, ``ham``, and ``bread`` configuration keys
 of the ``foo`` section to ``medium``, ``prosciutto``, and ``toasted``,
 respectively. As you can see there only thing that matters is the last
 value that was set for each of the configuration keys.
 
 If a configuration key is set multiple times in different
 configuration files the final value will depend on the order in which
 the different configuration files are read, with settings from earlier
 paths overriding later ones as described on the ``Files`` section
 above.
 
 A line of the form ``%include file`` will include ``file`` into the
 current configuration file. The inclusion is recursive, which means
 that included files can include other files. Filenames are relative to
 the configuration file in which the ``%include`` directive is found.
 Environment variables and ``~user`` constructs are expanded in
 ``file``. This lets you do something like::
 
   %include ~/.hgrc.d/$HOST.rc
 
 to include a different configuration file on each computer you use.
 
 A line with ``%unset name`` will remove ``name`` from the current
 section, if it has been set previously.
 
 The values are either free-form text strings, lists of text strings,
 or Boolean values. Boolean values can be set to true using any of "1",
 "yes", "true", or "on" and to false using "0", "no", "false", or "off"
 (all case insensitive).
 
 List values are separated by whitespace or comma, except when values are
 placed in double quotation marks::
 
   allow_read = "John Doe, PhD", brian, betty
 
 Quotation marks can be escaped by prefixing them with a backslash. Only
 quotation marks at the beginning of a word is counted as a quotation
 (e.g., ``foo"bar baz`` is the list of ``foo"bar`` and ``baz``).
 
 Sections
 ========
 
 This section describes the different sections that may appear in a
 Mercurial configuration file, the purpose of each section, its possible
 keys, and their possible values.
 
 ``alias``
 ---------
 
 Defines command aliases.
 Aliases allow you to define your own commands in terms of other
 commands (or aliases), optionally including arguments. Positional
 arguments in the form of ``$1``, ``$2``, etc in the alias definition
 are expanded by Mercurial before execution. Positional arguments not
 already used by ``$N`` in the definition are put at the end of the
 command to be executed.
 
 Alias definitions consist of lines of the form::
 
     <alias> = <command> [<argument>]...
 
 For example, this definition::
 
     latest = log --limit 5
 
 creates a new command ``latest`` that shows only the five most recent
 changesets. You can define subsequent aliases using earlier ones::
 
     stable5 = latest -b stable
 
 .. note::
 
    It is possible to create aliases with the same names as
    existing commands, which will then override the original
    definitions. This is almost always a bad idea!
 
 An alias can start with an exclamation point (``!``) to make it a
 shell alias. A shell alias is executed with the shell and will let you
 run arbitrary commands. As an example, ::
 
    echo = !echo $@
 
 will let you do ``hg echo foo`` to have ``foo`` printed in your
 terminal. A better example might be::
 
    purge = !$HG status --no-status --unknown -0 | xargs -0 rm
 
 which will make ``hg purge`` delete all unknown files in the
 repository in the same manner as the purge extension.
 
 Positional arguments like ``$1``, ``$2``, etc. in the alias definition
 expand to the command arguments. Unmatched arguments are
 removed. ``$0`` expands to the alias name and ``$@`` expands to all
 arguments separated by a space. These expansions happen before the
 command is passed to the shell.
 
 Shell aliases are executed in an environment where ``$HG`` expands to
 the path of the Mercurial that was used to execute the alias. This is
 useful when you want to call further Mercurial commands in a shell
 alias, as was done above for the purge alias. In addition,
 ``$HG_ARGS`` expands to the arguments given to Mercurial. In the ``hg
 echo foo`` call above, ``$HG_ARGS`` would expand to ``echo foo``.
 
 .. note::
 
    Some global configuration options such as ``-R`` are
    processed before shell aliases and will thus not be passed to
    aliases.
 
 
 ``annotate``
 ------------
 
 Settings used when displaying file annotations. All values are
 Booleans and default to False. See ``diff`` section for related
 options for the diff command.
 
 ``ignorews``
     Ignore white space when comparing lines.
 
 ``ignorewsamount``
     Ignore changes in the amount of white space.
 
 ``ignoreblanklines``
     Ignore changes whose lines are all blank.
 
 
 ``auth``
 --------
 
 Authentication credentials for HTTP authentication. This section
 allows you to store usernames and passwords for use when logging
 *into* HTTP servers. See the ``[web]`` configuration section if
 you want to configure *who* can login to your HTTP server.
 
 Each line has the following format::
 
     <name>.<argument> = <value>
 
 where ``<name>`` is used to group arguments into authentication
 entries. Example::
 
     foo.prefix = hg.intevation.org/mercurial
     foo.username = foo
     foo.password = bar
     foo.schemes = http https
 
     bar.prefix = secure.example.org
     bar.key = path/to/file.key
     bar.cert = path/to/file.cert
     bar.schemes = https
 
 Supported arguments:
 
 ``prefix``
     Either ``*`` or a URI prefix with or without the scheme part.
     The authentication entry with the longest matching prefix is used
     (where ``*`` matches everything and counts as a match of length
     1). If the prefix doesn't include a scheme, the match is performed
     against the URI with its scheme stripped as well, and the schemes
     argument, q.v., is then subsequently consulted.
 
 ``username``
     Optional. Username to authenticate with. If not given, and the
     remote site requires basic or digest authentication, the user will
     be prompted for it. Environment variables are expanded in the
     username letting you do ``foo.username = $USER``. If the URI
     includes a username, only ``[auth]`` entries with a matching
     username or without a username will be considered.
 
 ``password``
     Optional. Password to authenticate with. If not given, and the
     remote site requires basic or digest authentication, the user
     will be prompted for it.
 
 ``key``
     Optional. PEM encoded client certificate key file. Environment
     variables are expanded in the filename.
 
 ``cert``
     Optional. PEM encoded client certificate chain file. Environment
     variables are expanded in the filename.
 
 ``schemes``
     Optional. Space separated list of URI schemes to use this
     authentication entry with. Only used if the prefix doesn't include
     a scheme. Supported schemes are http and https. They will match
     static-http and static-https respectively, as well.
     Default: https.
 
 If no suitable authentication entry is found, the user is prompted
 for credentials as usual if required by the remote.
 
 
 ``decode/encode``
 -----------------
 
 Filters for transforming files on checkout/checkin. This would
 typically be used for newline processing or other
 localization/canonicalization of files.
 
 Filters consist of a filter pattern followed by a filter command.
 Filter patterns are globs by default, rooted at the repository root.
 For example, to match any file ending in ``.txt`` in the root
 directory only, use the pattern ``*.txt``. To match any file ending
 in ``.c`` anywhere in the repository, use the pattern ``**.c``.
 For each file only the first matching filter applies.
 
 The filter command can start with a specifier, either ``pipe:`` or
 ``tempfile:``. If no specifier is given, ``pipe:`` is used by default.
 
 A ``pipe:`` command must accept data on stdin and return the transformed
 data on stdout.
 
 Pipe example::
 
   [encode]
   # uncompress gzip files on checkin to improve delta compression
   # note: not necessarily a good idea, just an example
   *.gz = pipe: gunzip
 
   [decode]
   # recompress gzip files when writing them to the working dir (we
   # can safely omit "pipe:", because it's the default)
   *.gz = gzip
 
 A ``tempfile:`` command is a template. The string ``INFILE`` is replaced
 with the name of a temporary file that contains the data to be
 filtered by the command. The string ``OUTFILE`` is replaced with the name
 of an empty temporary file, where the filtered data must be written by
 the command.
 
 .. note::
 
    The tempfile mechanism is recommended for Windows systems,
    where the standard shell I/O redirection operators often have
    strange effects and may corrupt the contents of your files.
 
 This filter mechanism is used internally by the ``eol`` extension to
 translate line ending characters between Windows (CRLF) and Unix (LF)
 format. We suggest you use the ``eol`` extension for convenience.
 
 
 ``defaults``
 ------------
 
 (defaults are deprecated. Don't use them. Use aliases instead)
 
 Use the ``[defaults]`` section to define command defaults, i.e. the
 default options/arguments to pass to the specified commands.
 
 The following example makes :hg:`log` run in verbose mode, and
 :hg:`status` show only the modified files, by default::
 
   [defaults]
   log = -v
   status = -m
 
 The actual commands, instead of their aliases, must be used when
 defining command defaults. The command defaults will also be applied
 to the aliases of the commands defined.
 
 
 ``diff``
 --------
 
 Settings used when displaying diffs. Everything except for ``unified``
 is a Boolean and defaults to False. See ``annotate`` section for
 related options for the annotate command.
 
 ``git``
     Use git extended diff format.
 
 ``nodates``
     Don't include dates in diff headers.
 
 ``showfunc``
     Show which function each change is in.
 
 ``ignorews``
     Ignore white space when comparing lines.
 
 ``ignorewsamount``
     Ignore changes in the amount of white space.
 
 ``ignoreblanklines``
     Ignore changes whose lines are all blank.
 
 ``unified``
     Number of lines of context to show.
 
 ``email``
 ---------
 
 Settings for extensions that send email messages.
 
 ``from``
     Optional. Email address to use in "From" header and SMTP envelope
     of outgoing messages.
 
 ``to``
     Optional. Comma-separated list of recipients' email addresses.
 
 ``cc``
     Optional. Comma-separated list of carbon copy recipients'
     email addresses.
 
 ``bcc``
     Optional. Comma-separated list of blind carbon copy recipients'
     email addresses.
 
 ``method``
     Optional. Method to use to send email messages. If value is ``smtp``
     (default), use SMTP (see the ``[smtp]`` section for configuration).
     Otherwise, use as name of program to run that acts like sendmail
     (takes ``-f`` option for sender, list of recipients on command line,
     message on stdin). Normally, setting this to ``sendmail`` or
     ``/usr/sbin/sendmail`` is enough to use sendmail to send messages.
 
 ``charsets``
     Optional. Comma-separated list of character sets considered
     convenient for recipients. Addresses, headers, and parts not
     containing patches of outgoing messages will be encoded in the
     first character set to which conversion from local encoding
     (``$HGENCODING``, ``ui.fallbackencoding``) succeeds. If correct
     conversion fails, the text in question is sent as is. Defaults to
     empty (explicit) list.
 
     Order of outgoing email character sets:
 
     1. ``us-ascii``: always first, regardless of settings
     2. ``email.charsets``: in order given by user
     3. ``ui.fallbackencoding``: if not in email.charsets
     4. ``$HGENCODING``: if not in email.charsets
     5. ``utf-8``: always last, regardless of settings
 
 Email example::
 
   [email]
   from = Joseph User <[e-mail]>
   method = /usr/sbin/sendmail
   # charsets for western Europeans
   # us-ascii, utf-8 omitted, as they are tried first and last
   charsets = iso-8859-1, iso-8859-15, windows-1252
 
 
 ``extensions``
 --------------
 
 Mercurial has an extension mechanism for adding new features. To
 enable an extension, create an entry for it in this section.
 
 If you know that the extension is already in Python's search path,
 you can give the name of the module, followed by ``=``, with nothing
 after the ``=``.
 
 Otherwise, give a name that you choose, followed by ``=``, followed by
 the path to the ``.py`` file (including the file name extension) that
 defines the extension.
 
 To explicitly disable an extension that is enabled in an hgrc of
 broader scope, prepend its path with ``!``, as in ``foo = !/ext/path``
 or ``foo = !`` when path is not supplied.
 
 Example for ``~/.hgrc``::
 
   [extensions]
   # (the progress extension will get loaded from Mercurial's path)
   progress =
   # (this extension will get loaded from the file specified)
   myfeature = ~/.hgext/myfeature.py
 
 
 ``format``
 ----------
 
 ``usestore``
     Enable or disable the "store" repository format which improves
     compatibility with systems that fold case or otherwise mangle
     filenames. Enabled by default. Disabling this option will allow
     you to store longer filenames in some situations at the expense of
     compatibility and ensures that the on-disk format of newly created
     repositories will be compatible with Mercurial before version 0.9.4.
 
 ``usefncache``
     Enable or disable the "fncache" repository format which enhances
     the "store" repository format (which has to be enabled to use
     fncache) to allow longer filenames and avoids using Windows
     reserved names, e.g. "nul". Enabled by default. Disabling this
     option ensures that the on-disk format of newly created
     repositories will be compatible with Mercurial before version 1.1.
 
 ``dotencode``
     Enable or disable the "dotencode" repository format which enhances
     the "fncache" repository format (which has to be enabled to use
     dotencode) to avoid issues with filenames starting with ._ on
     Mac OS X and spaces on Windows. Enabled by default. Disabling this
     option ensures that the on-disk format of newly created
     repositories will be compatible with Mercurial before version 1.7.
 
 ``graph``
 ---------
 
 Web graph view configuration. This section let you change graph
 elements display properties by branches, for instance to make the
 ``default`` branch stand out.
 
 Each line has the following format::
 
     <branch>.<argument> = <value>
 
 where ``<branch>`` is the name of the branch being
 customized. Example::
 
     [graph]
     # 2px width
     default.width = 2
     # red color
     default.color = FF0000
 
 Supported arguments:
 
 ``width``
     Set branch edges width in pixels.
 
 ``color``
     Set branch edges color in hexadecimal RGB notation.
 
 ``hooks``
 ---------
 
 Commands or Python functions that get automatically executed by
 various actions such as starting or finishing a commit. Multiple
 hooks can be run for the same action by appending a suffix to the
 action. Overriding a site-wide hook can be done by changing its
 value or setting it to an empty string.  Hooks can be prioritized
 by adding a prefix of ``priority`` to the hook name on a new line
 and setting the priority.  The default priority is 0 if
 not specified.
 
 Example ``.hg/hgrc``::
 
   [hooks]
   # update working directory after adding changesets
   changegroup.update = hg update
   # do not use the site-wide hook
   incoming =
   incoming.email = /my/email/hook
   incoming.autobuild = /my/build/hook
   # force autobuild hook to run before other incoming hooks
   priority.incoming.autobuild = 1
 
 Most hooks are run with environment variables set that give useful
 additional information. For each hook below, the environment
 variables it is passed are listed with names of the form ``$HG_foo``.
 
 ``changegroup``
   Run after a changegroup has been added via push, pull or unbundle.
   ID of the first new changeset is in ``$HG_NODE``. URL from which
   changes came is in ``$HG_URL``.
 
 ``commit``
   Run after a changeset has been created in the local repository. ID
   of the newly created changeset is in ``$HG_NODE``. Parent changeset
   IDs are in ``$HG_PARENT1`` and ``$HG_PARENT2``.
 
 ``incoming``
   Run after a changeset has been pulled, pushed, or unbundled into
   the local repository. The ID of the newly arrived changeset is in
   ``$HG_NODE``. URL that was source of changes came is in ``$HG_URL``.
 
 ``outgoing``
   Run after sending changes from local repository to another. ID of
   first changeset sent is in ``$HG_NODE``. Source of operation is in
   ``$HG_SOURCE``; see "preoutgoing" hook for description.
 
 ``post-<command>``
   Run after successful invocations of the associated command. The
   contents of the command line are passed as ``$HG_ARGS`` and the result
   code in ``$HG_RESULT``. Parsed command line arguments are passed as
   ``$HG_PATS`` and ``$HG_OPTS``. These contain string representations of
   the python data internally passed to <command>. ``$HG_OPTS`` is a
   dictionary of options (with unspecified options set to their defaults).
   ``$HG_PATS`` is a list of arguments. Hook failure is ignored.
 
 ``pre-<command>``
   Run before executing the associated command. The contents of the
   command line are passed as ``$HG_ARGS``. Parsed command line arguments
   are passed as ``$HG_PATS`` and ``$HG_OPTS``. These contain string
   representations of the data internally passed to <command>. ``$HG_OPTS``
   is a  dictionary of options (with unspecified options set to their
   defaults). ``$HG_PATS`` is a list of arguments. If the hook returns
   failure, the command doesn't execute and Mercurial returns the failure
   code.
 
 ``prechangegroup``
   Run before a changegroup is added via push, pull or unbundle. Exit
   status 0 allows the changegroup to proceed. Non-zero status will
   cause the push, pull or unbundle to fail. URL from which changes
   will come is in ``$HG_URL``.
 
 ``precommit``
   Run before starting a local commit. Exit status 0 allows the
   commit to proceed. Non-zero status will cause the commit to fail.
   Parent changeset IDs are in ``$HG_PARENT1`` and ``$HG_PARENT2``.
 
 ``prelistkeys``
   Run before listing pushkeys (like bookmarks) in the
   repository. Non-zero status will cause failure. The key namespace is
   in ``$HG_NAMESPACE``.
 
 ``preoutgoing``
   Run before collecting changes to send from the local repository to
   another. Non-zero status will cause failure. This lets you prevent
   pull over HTTP or SSH. Also prevents against local pull, push
   (outbound) or bundle commands, but not effective, since you can
   just copy files instead then. Source of operation is in
   ``$HG_SOURCE``. If "serve", operation is happening on behalf of remote
   SSH or HTTP repository. If "push", "pull" or "bundle", operation
   is happening on behalf of repository on same system.
 
 ``prepushkey``
   Run before a pushkey (like a bookmark) is added to the
   repository. Non-zero status will cause the key to be rejected. The
   key namespace is in ``$HG_NAMESPACE``, the key is in ``$HG_KEY``,
   the old value (if any) is in ``$HG_OLD``, and the new value is in
   ``$HG_NEW``.
 
 ``pretag``
   Run before creating a tag. Exit status 0 allows the tag to be
   created. Non-zero status will cause the tag to fail. ID of
   changeset to tag is in ``$HG_NODE``. Name of tag is in ``$HG_TAG``. Tag is
   local if ``$HG_LOCAL=1``, in repository if ``$HG_LOCAL=0``.
 
 ``pretxnchangegroup``
   Run after a changegroup has been added via push, pull or unbundle,
   but before the transaction has been committed. Changegroup is
   visible to hook program. This lets you validate incoming changes
   before accepting them. Passed the ID of the first new changeset in
   ``$HG_NODE``. Exit status 0 allows the transaction to commit. Non-zero
   status will cause the transaction to be rolled back and the push,
   pull or unbundle will fail. URL that was source of changes is in
   ``$HG_URL``.
 
 ``pretxncommit``
   Run after a changeset has been created but the transaction not yet
   committed. Changeset is visible to hook program. This lets you
   validate commit message and changes. Exit status 0 allows the
   commit to proceed. Non-zero status will cause the transaction to
   be rolled back. ID of changeset is in ``$HG_NODE``. Parent changeset
   IDs are in ``$HG_PARENT1`` and ``$HG_PARENT2``.
 
 ``preupdate``
   Run before updating the working directory. Exit status 0 allows
   the update to proceed. Non-zero status will prevent the update.
   Changeset ID of first new parent is in ``$HG_PARENT1``. If merge, ID
   of second new parent is in ``$HG_PARENT2``.
 
 ``listkeys``
   Run after listing pushkeys (like bookmarks) in the repository. The
   key namespace is in ``$HG_NAMESPACE``. ``$HG_VALUES`` is a
   dictionary containing the keys and values.
 
 ``pushkey``
   Run after a pushkey (like a bookmark) is added to the
   repository. The key namespace is in ``$HG_NAMESPACE``, the key is in
   ``$HG_KEY``, the old value (if any) is in ``$HG_OLD``, and the new
   value is in ``$HG_NEW``.
 
 ``tag``
   Run after a tag is created. ID of tagged changeset is in ``$HG_NODE``.
   Name of tag is in ``$HG_TAG``. Tag is local if ``$HG_LOCAL=1``, in
   repository if ``$HG_LOCAL=0``.
 
 ``update``
   Run after updating the working directory. Changeset ID of first
   new parent is in ``$HG_PARENT1``. If merge, ID of second new parent is
   in ``$HG_PARENT2``. If the update succeeded, ``$HG_ERROR=0``. If the
   update failed (e.g. because conflicts not resolved), ``$HG_ERROR=1``.
 
 .. note::
 
    It is generally better to use standard hooks rather than the
    generic pre- and post- command hooks as they are guaranteed to be
    called in the appropriate contexts for influencing transactions.
    Also, hooks like "commit" will be called in all contexts that
    generate a commit (e.g. tag) and not just the commit command.
 
 .. note::
 
    Environment variables with empty values may not be passed to
    hooks on platforms such as Windows. As an example, ``$HG_PARENT2``
    will have an empty value under Unix-like platforms for non-merge
    changesets, while it will not be available at all under Windows.
 
 The syntax for Python hooks is as follows::
 
   hookname = python:modulename.submodule.callable
   hookname = python:/path/to/python/module.py:callable
 
 Python hooks are run within the Mercurial process. Each hook is
 called with at least three keyword arguments: a ui object (keyword
 ``ui``), a repository object (keyword ``repo``), and a ``hooktype``
 keyword that tells what kind of hook is used. Arguments listed as
 environment variables above are passed as keyword arguments, with no
 ``HG_`` prefix, and names in lower case.
 
 If a Python hook returns a "true" value or raises an exception, this
 is treated as a failure.
 
 
 ``hostfingerprints``
 --------------------
 
 Fingerprints of the certificates of known HTTPS servers.
 A HTTPS connection to a server with a fingerprint configured here will
 only succeed if the servers certificate matches the fingerprint.
 This is very similar to how ssh known hosts works.
 The fingerprint is the SHA-1 hash value of the DER encoded certificate.
 The CA chain and web.cacerts is not used for servers with a fingerprint.
 
 For example::
 
     [hostfingerprints]
     hg.intevation.org = fa:1f:d9:48:f1:e7:74:30:38:8d:d8:58:b6:94:b8:58:28:7d:8b:d0
 
 This feature is only supported when using Python 2.6 or later.
 
 
 ``http_proxy``
 --------------
 
 Used to access web-based Mercurial repositories through a HTTP
 proxy.
 
 ``host``
     Host name and (optional) port of the proxy server, for example
     "myproxy:8000".
 
 ``no``
     Optional. Comma-separated list of host names that should bypass
     the proxy.
 
 ``passwd``
     Optional. Password to authenticate with at the proxy server.
 
 ``user``
     Optional. User name to authenticate with at the proxy server.
 
 ``always``
     Optional. Always use the proxy, even for localhost and any entries
     in ``http_proxy.no``. True or False. Default: False.
 
 ``merge-patterns``
 ------------------
 
 This section specifies merge tools to associate with particular file
 patterns. Tools matched here will take precedence over the default
 merge tool. Patterns are globs by default, rooted at the repository
 root.
 
 Example::
 
   [merge-patterns]
   **.c = kdiff3
   **.jpg = myimgmerge
 
 ``merge-tools``
 ---------------
 
 This section configures external merge tools to use for file-level
-merges.
+merges. This section has likely been preconfigured at install time.
+Use :hg:`config merge-tools` to check the existing configuration.
+Also see :hg:`help merge-tools` for more details.
 
 Example ``~/.hgrc``::
 
   [merge-tools]
   # Override stock tool location
   kdiff3.executable = ~/bin/kdiff3
   # Specify command line
   kdiff3.args = $base $local $other -o $output
   # Give higher priority
   kdiff3.priority = 1
 
   # Define new tool
   myHtmlTool.args = -m $local $other $base $output
   myHtmlTool.regkey = Software\FooSoftware\HtmlMerge
   myHtmlTool.priority = 1
 
 Supported arguments:
 
 ``priority``
   The priority in which to evaluate this tool.
   Default: 0.
 
 ``executable``
   Either just the name of the executable or its pathname.  On Windows,
   the path can use environment variables with ${ProgramFiles} syntax.
   Default: the tool name.
 
 ``args``
   The arguments to pass to the tool executable. You can refer to the
   files being merged as well as the output file through these
   variables: ``$base``, ``$local``, ``$other``, ``$output``.
   Default: ``$local $base $other``
 
 ``premerge``
   Attempt to run internal non-interactive 3-way merge tool before
   launching external tool.  Options are ``true``, ``false``, or ``keep``
   to leave markers in the file if the premerge fails.
   Default: True
 
 ``binary``
   This tool can merge binary files. Defaults to False, unless tool
   was selected by file pattern match.
 
 ``symlink``
   This tool can merge symlinks. Defaults to False, even if tool was
   selected by file pattern match.
 
 ``check``
   A list of merge success-checking options:
 
   ``changed``
     Ask whether merge was successful when the merged file shows no changes.
   ``conflicts``
     Check whether there are conflicts even though the tool reported success.
   ``prompt``
     Always prompt for merge success, regardless of success reported by tool.
 
 ``fixeol``
   Attempt to fix up EOL changes caused by the merge tool.
   Default: False
 
 ``gui``
   This tool requires a graphical interface to run. Default: False
 
 ``regkey``
   Windows registry key which describes install location of this
   tool. Mercurial will search for this key first under
   ``HKEY_CURRENT_USER`` and then under ``HKEY_LOCAL_MACHINE``.
   Default: None
 
 ``regkeyalt``
   An alternate Windows registry key to try if the first key is not
   found.  The alternate key uses the same ``regname`` and ``regappend``
   semantics of the primary key.  The most common use for this key
   is to search for 32bit applications on 64bit operating systems.
   Default: None
 
 ``regname``
   Name of value to read from specified registry key. Defaults to the
   unnamed (default) value.
 
 ``regappend``
   String to append to the value read from the registry, typically
   the executable name of the tool.
   Default: None
 
 
 ``patch``
 ---------
 
 Settings used when applying patches, for instance through the 'import'
 command or with Mercurial Queues extension.
 
 ``eol``
     When set to 'strict' patch content and patched files end of lines
     are preserved. When set to ``lf`` or ``crlf``, both files end of
     lines are ignored when patching and the result line endings are
     normalized to either LF (Unix) or CRLF (Windows). When set to
     ``auto``, end of lines are again ignored while patching but line
     endings in patched files are normalized to their original setting
     on a per-file basis. If target file does not exist or has no end
     of line, patch line endings are preserved.
     Default: strict.
 
 
 ``paths``
 ---------
 
 Assigns symbolic names to repositories. The left side is the
 symbolic name, and the right gives the directory or URL that is the
 location of the repository. Default paths can be declared by setting
 the following entries.
 
 ``default``
     Directory or URL to use when pulling if no source is specified.
     Default is set to repository from which the current repository was
     cloned.
 
 ``default-push``
     Optional. Directory or URL to use when pushing if no destination
     is specified.
 
 Custom paths can be defined by assigning the path to a name that later can be
 used from the command line. Example::
 
     [paths]
     my_path = http://example.com/path
 
 To push to the path defined in ``my_path`` run the command::
 
     hg push my_path
 
 
 ``phases``
 ----------
 
 Specifies default handling of phases. See :hg:`help phases` for more
 information about working with phases.
 
 ``publish``
     Controls draft phase behavior when working as a server. When true,
     pushed changesets are set to public in both client and server and
     pulled or cloned changesets are set to public in the client.
     Default: True
 
 ``new-commit``
     Phase of newly-created commits.
     Default: draft
 
 ``checksubrepos``
     Check the phase of the current revision of each subrepository. Allowed
     values are "ignore", "follow" and "abort". For settings other than
     "ignore", the phase of the current revision of each subrepository is
     checked before committing the parent repository. If any of those phases is
     greater than the phase of the parent repository (e.g. if a subrepo is in a
     "secret" phase while the parent repo is in "draft" phase), the commit is
     either aborted (if checksubrepos is set to "abort") or the higher phase is
     used for the parent repository commit (if set to "follow").
     Default: "follow"
 
 
 ``profiling``
 -------------
 
 Specifies profiling type, format, and file output. Two profilers are
 supported: an instrumenting profiler (named ``ls``), and a sampling
 profiler (named ``stat``).
 
 In this section description, 'profiling data' stands for the raw data
 collected during profiling, while 'profiling report' stands for a
 statistical text report generated from the profiling data. The
 profiling is done using lsprof.
 
 ``type``
     The type of profiler to use.
     Default: ls.
 
     ``ls``
       Use Python's built-in instrumenting profiler. This profiler
       works on all platforms, but each line number it reports is the
       first line of a function. This restriction makes it difficult to
       identify the expensive parts of a non-trivial function.
     ``stat``
       Use a third-party statistical profiler, statprof. This profiler
       currently runs only on Unix systems, and is most useful for
       profiling commands that run for longer than about 0.1 seconds.
 
 ``format``
     Profiling format.  Specific to the ``ls`` instrumenting profiler.
     Default: text.
 
     ``text``
       Generate a profiling report. When saving to a file, it should be
       noted that only the report is saved, and the profiling data is
       not kept.
     ``kcachegrind``
       Format profiling data for kcachegrind use: when saving to a
       file, the generated file can directly be loaded into
       kcachegrind.
 
 ``frequency``
     Sampling frequency.  Specific to the ``stat`` sampling profiler.
     Default: 1000.
 
 ``output``
     File path where profiling data or report should be saved. If the
     file exists, it is replaced. Default: None, data is printed on
     stderr
 
 ``sort``
     Sort field.  Specific to the ``ls`` instrumenting profiler.
     One of ``callcount``, ``reccallcount``, ``totaltime`` and
     ``inlinetime``.
     Default: inlinetime.
 
 ``limit``
     Number of lines to show. Specific to the ``ls`` instrumenting profiler.
     Default: 30.
 
 ``nested``
     Show at most this number of lines of drill-down info after each main entry.
     This can help explain the difference between Total and Inline.
     Specific to the ``ls`` instrumenting profiler.
     Default: 5.
 
 ``revsetalias``
 ---------------
 
 Alias definitions for revsets. See :hg:`help revsets` for details.
 
 ``server``
 ----------
 
 Controls generic server settings.
 
 ``uncompressed``
     Whether to allow clients to clone a repository using the
     uncompressed streaming protocol. This transfers about 40% more
     data than a regular clone, but uses less memory and CPU on both
     server and client. Over a LAN (100 Mbps or better) or a very fast
     WAN, an uncompressed streaming clone is a lot faster (~10x) than a
     regular clone. Over most WAN connections (anything slower than
     about 6 Mbps), uncompressed streaming is slower, because of the
     extra data transfer overhead. This mode will also temporarily hold
     the write lock while determining what data to transfer.
     Default is True.
 
 ``preferuncompressed``
     When set, clients will try to use the uncompressed streaming
     protocol. Default is False.
 
 ``validate``
     Whether to validate the completeness of pushed changesets by
     checking that all new file revisions specified in manifests are
     present. Default is False.
 
 ``smtp``
 --------
 
 Configuration for extensions that need to send email messages.
 
 ``host``
     Host name of mail server, e.g. "mail.example.com".
 
 ``port``
     Optional. Port to connect to on mail server. Default: 465 (if
     ``tls`` is smtps) or 25 (otherwise).
 
 ``tls``
     Optional. Method to enable TLS when connecting to mail server: starttls,
     smtps or none. Default: none.
 
 ``verifycert``
     Optional. Verification for the certificate of mail server, when
     ``tls`` is starttls or smtps. "strict", "loose" or False. For
     "strict" or "loose", the certificate is verified as same as the
     verification for HTTPS connections (see ``[hostfingerprints]`` and
     ``[web] cacerts`` also). For "strict", sending email is also
     aborted, if there is no configuration for mail server in
     ``[hostfingerprints]`` and ``[web] cacerts``.  --insecure for
     :hg:`email` overwrites this as "loose". Default: "strict".
 
 ``username``
     Optional. User name for authenticating with the SMTP server.
     Default: none.
 
 ``password``
     Optional. Password for authenticating with the SMTP server. If not
     specified, interactive sessions will prompt the user for a
     password; non-interactive sessions will fail. Default: none.
 
 ``local_hostname``
     Optional. It's the hostname that the sender can use to identify
     itself to the MTA.
 
 
 ``subpaths``
 ------------
 
 Subrepository source URLs can go stale if a remote server changes name
 or becomes temporarily unavailable. This section lets you define
 rewrite rules of the form::
 
     <pattern> = <replacement>
 
 where ``pattern`` is a regular expression matching a subrepository
 source URL and ``replacement`` is the replacement string used to
 rewrite it. Groups can be matched in ``pattern`` and referenced in
 ``replacements``. For instance::
 
     http://server/(.*)-hg/ = http://hg.server/\1/
 
 rewrites ``http://server/foo-hg/`` into ``http://hg.server/foo/``.
 
 Relative subrepository paths are first made absolute, and the
 rewrite rules are then applied on the full (absolute) path. The rules
 are applied in definition order.
 
 ``trusted``
 -----------
 
 Mercurial will not use the settings in the
 ``.hg/hgrc`` file from a repository if it doesn't belong to a trusted
 user or to a trusted group, as various hgrc features allow arbitrary
 commands to be run. This issue is often encountered when configuring
 hooks or extensions for shared repositories or servers. However,
 the web interface will use some safe settings from the ``[web]``
 section.
 
 This section specifies what users and groups are trusted. The
 current user is always trusted. To trust everybody, list a user or a
 group with name ``*``. These settings must be placed in an
 *already-trusted file* to take effect, such as ``$HOME/.hgrc`` of the
 user or service running Mercurial.
 
 ``users``
   Comma-separated list of trusted users.
 
 ``groups``
   Comma-separated list of trusted groups.
 
 
 ``ui``
 ------
 
 User interface controls.
 
 ``archivemeta``
     Whether to include the .hg_archival.txt file containing meta data
     (hashes for the repository base and for tip) in archives created
     by the :hg:`archive` command or downloaded via hgweb.
     Default is True.
 
 ``askusername``
     Whether to prompt for a username when committing. If True, and
     neither ``$HGUSER`` nor ``$EMAIL`` has been specified, then the user will
     be prompted to enter a username. If no username is entered, the
     default ``USER@HOST`` is used instead.
     Default is False.
 
 ``commitsubrepos``
     Whether to commit modified subrepositories when committing the
     parent repository. If False and one subrepository has uncommitted
     changes, abort the commit.
     Default is False.
 
 ``debug``
     Print debugging information. True or False. Default is False.
 
 ``editor``
     The editor to use during a commit. Default is ``$EDITOR`` or ``vi``.
 
 ``fallbackencoding``
     Encoding to try if it's not possible to decode the changelog using
     UTF-8. Default is ISO-8859-1.
 
 ``ignore``
     A file to read per-user ignore patterns from. This file should be
     in the same format as a repository-wide .hgignore file. This
     option supports hook syntax, so if you want to specify multiple
     ignore files, you can do so by setting something like
     ``ignore.other = ~/.hgignore2``. For details of the ignore file
     format, see the ``hgignore(5)`` man page.
 
 ``interactive``
     Allow to prompt the user. True or False. Default is True.
 
 ``logtemplate``
     Template string for commands that print changesets.
 
 ``merge``
     The conflict resolution program to use during a manual merge.
     For more information on merge tools see :hg:`help merge-tools`.
     For configuring merge tools see the ``[merge-tools]`` section.
 
 ``portablefilenames``
     Check for portable filenames. Can be ``warn``, ``ignore`` or ``abort``.
     Default is ``warn``.
     If set to ``warn`` (or ``true``), a warning message is printed on POSIX
     platforms, if a file with a non-portable filename is added (e.g. a file
     with a name that can't be created on Windows because it contains reserved
     parts like ``AUX``, reserved characters like ``:``, or would cause a case
     collision with an existing file).
     If set to ``ignore`` (or ``false``), no warning is printed.
     If set to ``abort``, the command is aborted.
     On Windows, this configuration option is ignored and the command aborted.
 
 ``quiet``
     Reduce the amount of output printed. True or False. Default is False.
 
 ``remotecmd``
     remote command to use for clone/push/pull operations. Default is ``hg``.
 
 ``reportoldssl``
     Warn if an SSL certificate is unable to be due to using Python
     2.5 or earlier. True or False. Default is True.
 
 ``report_untrusted``
     Warn if a ``.hg/hgrc`` file is ignored due to not being owned by a
     trusted user or group. True or False. Default is True.
 
 ``slash``
     Display paths using a slash (``/``) as the path separator. This
     only makes a difference on systems where the default path
     separator is not the slash character (e.g. Windows uses the
     backslash character (``\``)).
     Default is False.
 
 ``ssh``
     command to use for SSH connections. Default is ``ssh``.
 
 ``strict``
     Require exact command names, instead of allowing unambiguous
     abbreviations. True or False. Default is False.
 
 ``style``
     Name of style to use for command output.
 
 ``timeout``
     The timeout used when a lock is held (in seconds), a negative value
     means no timeout. Default is 600.
 
 ``traceback``
     Mercurial always prints a traceback when an unknown exception
     occurs. Setting this to True will make Mercurial print a traceback
     on all exceptions, even those recognized by Mercurial (such as
     IOError or MemoryError). Default is False.
 
 ``username``
     The committer of a changeset created when running "commit".
     Typically a person's name and email address, e.g. ``Fred Widget
     <[e-mail]>``. Default is ``$EMAIL`` or ``username@hostname``. If
     the username in hgrc is empty, it has to be specified manually or
     in a different hgrc file (e.g. ``$HOME/.hgrc``, if the admin set
     ``username =``  in the system hgrc). Environment variables in the
     username are expanded.
 
 ``verbose``
     Increase the amount of output printed. True or False. Default is False.
 
 
 ``web``
 -------
 
 Web interface configuration. The settings in this section apply to
 both the builtin webserver (started by :hg:`serve`) and the script you
 run through a webserver (``hgweb.cgi`` and the derivatives for FastCGI
 and WSGI).
 
 The Mercurial webserver does no authentication (it does not prompt for
 usernames and passwords to validate *who* users are), but it does do
 authorization (it grants or denies access for *authenticated users*
 based on settings in this section). You must either configure your
 webserver to do authentication for you, or disable the authorization
 checks.
 
 For a quick setup in a trusted environment, e.g., a private LAN, where
 you want it to accept pushes from anybody, you can use the following
 command line::
 
     $ hg --config web.allow_push=* --config web.push_ssl=False serve
 
 Note that this will allow anybody to push anything to the server and
 that this should not be used for public servers.
 
 The full set of options is:
 
 ``accesslog``
     Where to output the access log. Default is stdout.
 
 ``address``
     Interface address to bind to. Default is all.
 
 ``allow_archive``
     List of archive format (bz2, gz, zip) allowed for downloading.
     Default is empty.
 
 ``allowbz2``
     (DEPRECATED) Whether to allow .tar.bz2 downloading of repository
     revisions.
     Default is False.
 
 ``allowgz``
     (DEPRECATED) Whether to allow .tar.gz downloading of repository
     revisions.
     Default is False.
 
 ``allowpull``
     Whether to allow pulling from the repository. Default is True.
 
 ``allow_push``
     Whether to allow pushing to the repository. If empty or not set,
     push is not allowed. If the special value ``*``, any remote user can
     push, including unauthenticated users. Otherwise, the remote user
     must have been authenticated, and the authenticated user name must
     be present in this list. The contents of the allow_push list are
     examined after the deny_push list.
 
 ``allow_read``
     If the user has not already been denied repository access due to
     the contents of deny_read, this list determines whether to grant
     repository access to the user. If this list is not empty, and the
     user is unauthenticated or not present in the list, then access is
     denied for the user. If the list is empty or not set, then access
     is permitted to all users by default. Setting allow_read to the
     special value ``*`` is equivalent to it not being set (i.e. access
     is permitted to all users). The contents of the allow_read list are
     examined after the deny_read list.
 
 ``allowzip``
     (DEPRECATED) Whether to allow .zip downloading of repository
     revisions. Default is False. This feature creates temporary files.
 
 ``archivesubrepos``
     Whether to recurse into subrepositories when archiving. Default is
     False.
 
 ``baseurl``
     Base URL to use when publishing URLs in other locations, so
     third-party tools like email notification hooks can construct
     URLs. Example: ``http://hgserver/repos/``.
 
 ``cacerts``
     Path to file containing a list of PEM encoded certificate
     authority certificates. Environment variables and ``~user``
     constructs are expanded in the filename. If specified on the
     client, then it will verify the identity of remote HTTPS servers
     with these certificates.
 
     This feature is only supported when using Python 2.6 or later. If you wish
     to use it with earlier versions of Python, install the backported
     version of the ssl library that is available from
     ``http://pypi.python.org``.
 
     To disable SSL verification temporarily, specify ``--insecure`` from
     command line.
 
     You can use OpenSSL's CA certificate file if your platform has
     one. On most Linux systems this will be
     ``/etc/ssl/certs/ca-certificates.crt``. Otherwise you will have to
     generate this file manually. The form must be as follows::
 
         -----BEGIN CERTIFICATE-----
         ... (certificate in base64 PEM encoding) ...
         -----END CERTIFICATE-----
         -----BEGIN CERTIFICATE-----
         ... (certificate in base64 PEM encoding) ...
         -----END CERTIFICATE-----
 
 ``cache``
     Whether to support caching in hgweb. Defaults to True.
 
 ``collapse``
     With ``descend`` enabled, repositories in subdirectories are shown at
     a single level alongside repositories in the current path. With
     ``collapse`` also enabled, repositories residing at a deeper level than
     the current path are grouped behind navigable directory entries that
     lead to the locations of these repositories. In effect, this setting
     collapses each collection of repositories found within a subdirectory
     into a single entry for that subdirectory. Default is False.
 
 ``comparisoncontext``
     Number of lines of context to show in side-by-side file comparison. If
     negative or the value ``full``, whole files are shown. Default is 5.
     This setting can be overridden by a ``context`` request parameter to the
     ``comparison`` command, taking the same values.
 
 ``contact``
     Name or email address of the person in charge of the repository.
     Defaults to ui.username or ``$EMAIL`` or "unknown" if unset or empty.
 
 ``deny_push``
     Whether to deny pushing to the repository. If empty or not set,
     push is not denied. If the special value ``*``, all remote users are
     denied push. Otherwise, unauthenticated users are all denied, and
     any authenticated user name present in this list is also denied. The
     contents of the deny_push list are examined before the allow_push list.
 
 ``deny_read``
     Whether to deny reading/viewing of the repository. If this list is
     not empty, unauthenticated users are all denied, and any
     authenticated user name present in this list is also denied access to
     the repository. If set to the special value ``*``, all remote users
     are denied access (rarely needed ;). If deny_read is empty or not set,
     the determination of repository access depends on the presence and
     content of the allow_read list (see description). If both
     deny_read and allow_read are empty or not set, then access is
     permitted to all users by default. If the repository is being
     served via hgwebdir, denied users will not be able to see it in
     the list of repositories. The contents of the deny_read list have
     priority over (are examined before) the contents of the allow_read
     list.
 
 ``descend``
     hgwebdir indexes will not descend into subdirectories. Only repositories
     directly in the current path will be shown (other repositories are still
     available from the index corresponding to their containing path).
 
 ``description``
     Textual description of the repository's purpose or contents.
     Default is "unknown".
 
 ``encoding``
     Character encoding name. Default is the current locale charset.
     Example: "UTF-8"
 
 ``errorlog``
     Where to output the error log. Default is stderr.
 
 ``guessmime``
     Control MIME types for raw download of file content.
     Set to True to let hgweb guess the content type from the file
     extension. This will serve HTML files as ``text/html`` and might
     allow cross-site scripting attacks when serving untrusted
     repositories. Default is False.
 
 ``hidden``
     Whether to hide the repository in the hgwebdir index.
     Default is False.
 
 ``ipv6``
     Whether to use IPv6. Default is False.
 
 ``logoimg``
     File name of the logo image that some templates display on each page.
     The file name is relative to ``staticurl``. That is, the full path to
     the logo image is "staticurl/logoimg".
     If unset, ``hglogo.png`` will be used.
 
 ``logourl``
     Base URL to use for logos. If unset, ``http://mercurial.selenic.com/``
     will be used.
 
 ``maxchanges``
     Maximum number of changes to list on the changelog. Default is 10.
 
 ``maxfiles``
     Maximum number of files to list per changeset. Default is 10.
 
 ``maxshortchanges``
     Maximum number of changes to list on the shortlog, graph or filelog
     pages. Default is 60.
 
 ``name``
     Repository name to use in the web interface. Default is current
     working directory.
 
 ``port``
     Port to listen on. Default is 8000.
 
 ``prefix``
     Prefix path to serve from. Default is '' (server root).
 
 ``push_ssl``
     Whether to require that inbound pushes be transported over SSL to
     prevent password sniffing. Default is True.
 
 ``staticurl``
     Base URL to use for static files. If unset, static files (e.g. the
     hgicon.png favicon) will be served by the CGI script itself. Use
     this setting to serve them directly with the HTTP server.
     Example: ``http://hgserver/static/``.
 
 ``stripes``
     How many lines a "zebra stripe" should span in multi-line output.
     Default is 1; set to 0 to disable.
 
 ``style``
     Which template map style to use.
 
 ``templates``
     Where to find the HTML templates. Default is install path.
 
 ``websub``
 ----------
 
 Web substitution filter definition. You can use this section to
 define a set of regular expression substitution patterns which
 let you automatically modify the hgweb server output.
 
 The default hgweb templates only apply these substitution patterns
 on the revision description fields. You can apply them anywhere
 you want when you create your own templates by adding calls to the
 "websub" filter (usually after calling the "escape" filter).
 
 This can be used, for example, to convert issue references to links
 to your issue tracker, or to convert "markdown-like" syntax into
 HTML (see the examples below).
 
 Each entry in this section names a substitution filter.
 The value of each entry defines the substitution expression itself.
 The websub expressions follow the old interhg extension syntax,
 which in turn imitates the Unix sed replacement syntax::
 
     patternname = s/SEARCH_REGEX/REPLACE_EXPRESSION/[i]
 
 You can use any separator other than "/". The final "i" is optional
 and indicates that the search must be case insensitive.
 
 Examples::
 
     [websub]
     issues = s|issue(\d+)|<a href="http://bts.example.org/issue\1">issue\1</a>|i
     italic = s/\b_(\S+)_\b/<i>\1<\/i>/
     bold = s/\*\b(\S+)\b\*/<b>\1<\/b>/
 
 ``worker``
 ----------
 
 Parallel master/worker configuration. We currently perform working
 directory updates in parallel on Unix-like systems, which greatly
 helps performance.
 
 ``numcpus``
     Number of CPUs to use for parallel operations. Default is 4 or the
     number of CPUs on the system, whichever is larger. A zero or
     negative value is treated as ``use the default``.