doc: add note about pattern rooted/unrooted cases to "hgignore" and "patterns"

each help topics describe that patterns are "not rooted" and "rooted"
in themselves, but not describe about each other.

so, this may causes misunderstanding about "rooted"-ness of patterns.

mercurial/help/hgignore.txt

@@ -1,80 +1,84 b''
 Synopsis
 --------
 
 The Mercurial system uses a file called ``.hgignore`` in the root
 directory of a repository to control its behavior when it searches
 for files that it is not currently tracking.
 
 Description
 -----------
 
 The working directory of a Mercurial repository will often contain
 files that should not be tracked by Mercurial. These include backup
 files created by editors and build products created by compilers.
 These files can be ignored by listing them in a ``.hgignore`` file in
 the root of the working directory. The ``.hgignore`` file must be
 created manually. It is typically put under version control, so that
 the settings will propagate to other repositories with push and pull.
 
 An untracked file is ignored if its path relative to the repository
 root directory, or any prefix path of that path, is matched against
 any pattern in ``.hgignore``.
 
 For example, say we have an untracked file, ``file.c``, at
 ``a/b/file.c`` inside our repository. Mercurial will ignore ``file.c``
 if any pattern in ``.hgignore`` matches ``a/b/file.c``, ``a/b`` or ``a``.
 
 In addition, a Mercurial configuration file can reference a set of
 per-user or global ignore files. See the ``ignore`` configuration
 key on the ``[ui]`` section of :hg:`help config` for details of how to
 configure these files.
 
 To control Mercurial's handling of files that it manages, many
 commands support the ``-I`` and ``-X`` options; see
 :hg:`help <command>` and :hg:`help patterns` for details.
 
 Syntax
 ------
 
 An ignore file is a plain text file consisting of a list of patterns,
 with one pattern per line. Empty lines are skipped. The ``#``
 character is treated as a comment character, and the ``\`` character
 is treated as an escape character.
 
 Mercurial supports several pattern syntaxes. The default syntax used
 is Python/Perl-style regular expressions.
 
 To change the syntax used, use a line of the following form::
 
   syntax: NAME
 
 where ``NAME`` is one of the following:
 
 ``regexp``
   Regular expression, Python/Perl syntax.
 ``glob``
   Shell-style glob.
 
 The chosen syntax stays in effect when parsing all patterns that
 follow, until another syntax is selected.
 
 Neither glob nor regexp patterns are rooted. A glob-syntax pattern of
 the form ``*.c`` will match a file ending in ``.c`` in any directory,
 and a regexp pattern of the form ``\.c$`` will do the same. To root a
 regexp pattern, start it with ``^``.
 
+.. note::
+  Patterns specified in other than ``.hgignore`` are always rooted.
+  Please see :hg:`help patterns` for details.
+
 Example
 -------
 
 Here is an example ignore file. ::
 
   # use glob syntax.
   syntax: glob
 
   *.elc
   *.pyc
   *~
 
   # switch to regexp syntax.
   syntax: regexp
   ^\.pc/

mercurial/help/patterns.txt

@@ -1,53 +1,57 b''
 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.
 
+.. note::
+  Patterns specified in ``.hgignore`` are not rooted. Please see
+  :hg:`help hgignore` for details.
+
 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.
 
 To read name patterns from a file, use ``listfile:`` or ``listfile0:``.
 The latter expects null delimited patterns while the former expects line
 feeds. Each string read from the file is itself treated as a file
 pattern.
 
 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
 
 File examples::
 
   listfile:list.txt  read list from list.txt with one file pattern per line
   listfile0:list.txt read list from list.txt with null byte delimiters
 
 See also :hg:`help filesets`.