hgignore.5.txt: improved description of matching

Improved the description of the matching behavior used with .hgignore.
Made some minor language improvements.

doc/hgignore.5.txt

@@ -1,92 +1,98 b''
 HGIGNORE(5)
 ===========
 Vadim Gelfer <[e-mail]>
 :man source: Mercurial
 :man manual: Mercurial Manual
 
 NAME
 ----
 hgignore - syntax for Mercurial ignore files
 
 SYNOPSIS
 --------
 
 The Mercurial system uses a file called `.hgignore` in the root
-directory of a repository to control its behavior when it finds files
-that it is not currently managing.
+directory of a repository to control its behavior when it searches
+for files that it is not currently tracking.
 
 DESCRIPTION
 -----------
 
-Mercurial ignores every unmanaged file that matches any pattern in an
-ignore file. The patterns in an ignore file do not apply to files
-managed by Mercurial. To control Mercurial's handling of files that it
-manages, see the hg(1) man page. Look for the "-I" and "-X" options.
+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`.
 
-In addition, a Mercurial configuration file can point to a set of
+For example, say we have an 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 hgrc(5) man page for details
 of how to configure these files. Look for the "ignore" entry in the
 "ui" section.
 
+To control Mercurial's handling of files that it manages, see the
+hg(1) man page. Look for the "-I" and "-X" options.
+
 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 "`^`".
 
 EXAMPLE
 -------
 
 Here is an example ignore file.
 
   # use glob syntax.
   syntax: glob
 
   *.elc
   *.pyc
   *~
 
   # switch to regexp syntax.
   syntax: regexp
   ^\.pc/
 
 AUTHOR
 ------
 Vadim Gelfer <[e-mail]>
 
 Mercurial was written by Matt Mackall <[e-mail]>.
 
 SEE ALSO
 --------
 hg(1), hgrc(5)
 
 COPYING
 -------
 This manual page is copyright 2006 Vadim Gelfer.
 Mercurial is copyright 2005-2009 Matt Mackall.
 Free use of this software is granted under the terms of the GNU General
 Public License (GPL).