help: add "hg help config" topic
This is a condensed version of the first two sections of hgrc.5.txt.
After a slight upgrade of minirst, we can move the whole of hgrc.5.txt
into the config help topic and just let the man page include it.
Mercurial accepts several notations for identifying one or more files
at a time.
By default, Mercurial treats filenames as shell-style extended glob
patterns.
Alternate pattern notations must be specified explicitly.
To use a plain path name without any pattern matching, start it with
``path:``. These path names must completely match starting at the
current repository root.
To use an extended glob, start a name with ``glob:``. Globs are rooted
at the current directory; a glob such as ``*.c`` will only match files
in the current directory ending with ``.c``.
The supported glob syntax extensions are ``**`` to match any string
across path separators and ``{a,b}`` to mean "a or b".
To use a Perl/Python regular expression, start a name with ``re:``.
Regexp pattern matching is anchored at the root of the repository.
Plain examples::
path:foo/bar a name bar in a directory named foo in the root
of the repository
path:path:name a file or directory named "path:name"
Glob examples::
glob:*.c any name ending in ".c" in the current directory
*.c any name ending in ".c" in the current directory
**.c any name ending in ".c" in any subdirectory of the
current directory including itself.
foo/*.c any name ending in ".c" in the directory foo
foo/**.c any name ending in ".c" in any subdirectory of foo
including itself.
Regexp examples::
re:.*\.c$ any name ending in ".c", anywhere in the repository