man: document the notmuch configuration settings in notmuch-config(1)

At the risk of duplication between the man page and the configuration
file generated by default, document the notmuch configuration options
in the notmuch config man page.

Existing users of notmuch should not be expected to re-generate their
config file in order to get access to the documentation for new
configuration options.

Include some minor fixes and cleanups while at it.

man/man1/notmuch-config.1

@@ -1,6 +1,6 @@
 .TH NOTMUCH-CONFIG 1 2011-12-04 "Notmuch 0.10.2"
 .SH NAME
-notmuch-config \- Output a single part of a multipart MIME message.
+notmuch-config \- Access notmuch configuration file.
 .SH SYNOPSIS
 
 .B notmuch config get
@@ -16,34 +16,125 @@ The
 command can be used to get or set settings in the notmuch
 configuration file.
 
-.SS GET
+.RS 4
-
+.TP 4
+.B get
 The value of the specified configuration item is printed to stdout. If
-the item has multiple values, each value is separated by a newline
+the item has multiple values (it is a list), each value is separated
-character.
+by a newline character.
+.RE
 
-Available configuration items include at least
+.RS 4
-
+.TP 4
-	database.path
+.B set
-
+The specified configuration item is set to the given value. To specify
-	user.name
+a multiple-value item (a list), provide each value as a separate
-
-	user.primary_email
-
-	user.other_email
-
-	new.tags
-
-.SS SET
-
-The specified configuration item is set to the given value.  To
-specify a multiple-value item, provide each value as a separate
 command-line argument.
 
 If no values are provided, the specified configuration item will be
 removed from the configuration file.
 .RE
 
+The available configuration items are described below.
+
+.RS 4
+.TP 4
+.B database.path
+The top-level directory where your mail currently exists and to where
+mail will be delivered in the future. Files should be individual email
+messages. Notmuch will store its database within a sub-directory of
+the path configured here named
+.BR ".notmuch".
+.RE
+
+.RS 4
+.TP 4
+.B user.name
+Your full name.
+.RE
+
+.RS 4
+.TP 4
+.B user.primary_email
+Your primary email address.
+.RE
+
+.RS 4
+.TP 4
+.B user.other_email
+A list of other email addresses at which you receive email.
+.RE
+
+.RS 4
+.TP 4
+.B new.tags
+A list of tags that will be added to all messages incorporated by
+.BR "notmuch new".
+.RE
+
+.RS 4
+.TP 4
+.B new.ignore
+A list of file and directory names, without path, that will not be
+searched for messages by
+.BR "notmuch new".
+All the files and directories matching any of the names specified here
+will be ignored, regardless of the location in the mail store
+directory hierarchy.
+.RE
+
+.RS 4
+.TP 4
+.B search.exclude
+A list of tags that will be excluded from search results by
+default. Using an excluded tag in a query will override that
+exclusion.
+.RE
+
+.RS 4
+.TP 4
+.B maildir.synchronize_flags
+If true, then the following maildir flags (in message filenames) will
+be synchronized with the corresponding notmuch tags:
+
+  Flag    Tag
+  ----    -------
+  D       draft
+  F       flagged
+  P       passed
+  R       replied
+  S       unread (added when 'S' flag is not present)
+
+The
+.B notmuch new
+command will notice flag changes in filenames and update tags, while
+the
+.B notmuch tag
+and
+.B notmuch restore
+commands will notice tag changes and update flags in filenames.
+
+If there have been any changes in the maildir (new messages added, old
+ones removed or renamed, maildir flags changed, etc.), it is advisable
+to run
+.B notmuch new
+before
+.B notmuch tag
+or
+.B notmuch restore
+commands to ensure the tag changes are properly synchronized to the
+maildir flags, as the commands expect the database and maildir to be
+in sync.
+.RE
+
+.RE
+.SH ENVIRONMENT
+The following environment variables can be used to control the
+behavior of notmuch.
+.TP
+.B NOTMUCH_CONFIG
+Specifies the location of the notmuch configuration file. Notmuch will
+use ${HOME}/.notmuch\-config if this variable is not set.
 .SH SEE ALSO
 
 \fBnotmuch\fR(1), \fBnotmuch-count\fR(1),