doc: use manpage role references to external man pages

Using manpage role references generates helpful links in html
documentation, while retaining the same boldface style in the man
pages.

The external man page site is configurable. The Debian manpage site
seems like a good fit for Notmuch.

doc/conf.py

@@ -80,6 +80,11 @@ htmlhelp_basename = 'notmuchdoc'
 # Despite the name, this actually affects manual pages as well.
 html_use_smartypants = False
 
+# See:
+# - https://www.sphinx-doc.org/en/master/usage/configuration.html#confval-manpages_url
+# - https://manpages.debian.org/
+manpages_url = 'https://manpages.debian.org/{page}.{section}.html'
+
 # -- Options for manual page output ---------------------------------------
 
 # One entry per manual page. List of tuples

doc/man1/notmuch-address.rst

@@ -21,8 +21,8 @@ Supported options for **address** include
 ``--format=``\ (**json**\ \|\ **sexp**\ \|\ **text**\ \|\ **text0**)
     Presents the results in either JSON, S-Expressions, newline
     character separated plain-text (default), or null character
-    separated plain-text (compatible with **xargs(1)** -0 option where
-    available).
+    separated plain-text (compatible with :manpage:`xargs(1)` -0
+    option where available).
 
 ``--format-version=N``
     Use the specified structured output format version. This is

doc/man1/notmuch-dump.rst

@@ -27,7 +27,7 @@ the remaining arguments are search terms.
 Supported options for **dump** include
 
 ``--gzip``
-    Compress the output in a format compatible with **gzip(1)**.
+    Compress the output in a format compatible with :manpage:`gzip(1)`.
 
 ``--format=(sup|batch-tag)``
     Notmuch restore supports two plain text dump formats, both with
@@ -36,8 +36,8 @@ Supported options for **dump** include
     **batch-tag**
         The default **batch-tag** dump format is intended to more
         robust against malformed message-ids and tags containing
-        whitespace or non-\ **ascii(7)** characters. Each line has the
-        form::
+        whitespace or non-\ :manpage:`ascii(7)` characters. Each line
+        has the form::
 
 	  +<*encoded-tag*\ > +<*encoded-tag*\ > ... -- id:<*quoted-message-id*\ >
 
@@ -54,11 +54,11 @@ Supported options for **dump** include
 
     **sup**
         The **sup** dump file format is specifically chosen to be
-        compatible with the format of files produced by sup-dump. So
-        if you've previously been using sup for mail, then the
-        **notmuch restore** command provides you a way to import all
-        of your tags (or labels as sup calls them). Each line has the
-        following form::
+        compatible with the format of files produced by
+        :manpage:`sup-dump(1)`. So if you've previously been using sup
+        for mail, then the **notmuch restore** command provides you a
+        way to import all of your tags (or labels as sup calls
+        them). Each line has the following form::
 
           <*message-id*\ > **(** <*tag*\ > ... **)**
 

doc/man1/notmuch-emacs-mua.rst

@@ -41,8 +41,9 @@ Supported options for **emacs-mua** include
     Even if a window system is available, use the current terminal.
 
 ``--client``
-    Use **emacsclient**, rather than **emacs**. For **emacsclient** to
-    work, you need an already running Emacs with a server, or use
+    Use :manpage:`emacsclient(1)`, rather than
+    :manpage:`emacs(1)`. For :manpage:`emacsclient(1)` to work, you
+    need an already running Emacs with a server, or use
     ``--auto-daemon``.
 
 ``--auto-daemon``
@@ -60,9 +61,9 @@ Supported options for **emacs-mua** include
     Output the resulting elisp to stdout instead of evaluating it.
 
 The supported positional parameters and short options are a compatible
-subset of the **mutt** MUA command-line options. The options and
-positional parameters modifying the message can't be combined with the
-mailto: URL.
+subset of the :manpage:`mutt(1)` MUA command-line options. The options
+and positional parameters modifying the message can't be combined with
+the mailto: URL.
 
 Options may be specified multiple times.
 
@@ -78,4 +79,6 @@ ENVIRONMENT VARIABLES
 SEE ALSO
 ========
 
-**notmuch(1)**, **emacsclient(1)**, **mutt(1)**
+**notmuch(1)**,
+:manpage:`emacsclient(1)`,
+:manpage:`mutt(1)`

doc/man1/notmuch-reply.rst

@@ -86,7 +86,7 @@ Supported options for **reply** include
     Use ``false`` to avoid even automatic decryption.
 
     Non-automatic decryption expects a functioning
-    **gpg-agent(1)** to provide any needed credentials. Without
+    :manpage:`gpg-agent(1)` to provide any needed credentials. Without
     one, the decryption will likely fail.
 
     Default: ``auto``

doc/man1/notmuch-restore.rst

@@ -77,9 +77,9 @@ GZIPPED INPUT
 =============
 
 \ **notmuch restore** will detect if the input is compressed in
-**gzip(1)** format and automatically decompress it while reading. This
-detection does not depend on file naming and in particular works for
-standard input.
+:manpage:`gzip(1)` format and automatically decompress it while
+reading. This detection does not depend on file naming and in
+particular works for standard input.
 
 SEE ALSO
 ========

doc/man1/notmuch-search.rst

@@ -27,8 +27,8 @@ Supported options for **search** include
 ``--format=``\ (**json**\ \|\ **sexp**\ \|\ **text**\ \|\ **text0**)
     Presents the results in either JSON, S-Expressions, newline
     character separated plain-text (default), or null character
-    separated plain-text (compatible with **xargs(1)** -0 option where
-    available).
+    separated plain-text (compatible with :manpage:`xargs(1)` -0
+    option where available).
 
 ``--format-version=N``
     Use the specified structured output format version. This is

doc/man1/notmuch-show.rst

@@ -130,7 +130,7 @@ Supported options for **show** include
     Use ``false`` to avoid even automatic decryption.
 
     Non-automatic decryption (``stash`` or ``true``, in the absence of
-    a stashed session key) expects a functioning **gpg-agent(1)** to
+    a stashed session key) expects a functioning :manpage:`gpg-agent(1)` to
     provide any needed credentials. Without one, the decryption will
     fail.
 

doc/man1/notmuch.rst

@@ -90,7 +90,8 @@ will do its best to detect those and ignore them.
 Mail storage that uses mbox format, (where one mbox file contains many
 messages), will not work with notmuch. If that's how your mail is
 currently stored, it is recommended you first convert it to maildir
-format with a utility such as mb2md before running **notmuch setup .**
+format with a utility such as :manpage:`mb2md(1)` before running
+**notmuch setup**.
 
 Invoking ``notmuch`` with no command argument will run **setup** if the
 setup command has not previously been completed.
@@ -152,7 +153,7 @@ of notmuch.
 
 **NOTMUCH\_TALLOC\_REPORT**
     Location to write a talloc memory usage report. See
-    **talloc\_enable\_leak\_report\_full** in **talloc(3)** for more
+    **talloc\_enable\_leak\_report\_full** in :manpage:`talloc(3)` for more
     information.
 
 **NOTMUCH\_DEBUG\_QUERY**

doc/man7/notmuch-search-terms.rst

@@ -39,7 +39,7 @@ indicate user-supplied values).
 
 Some of the prefixes with <regex> forms can be also used to restrict
 the results to those whose value matches a regular expression (see
-**regex(7)**) delimited with //, for example::
+:manpage:`regex(7)`) delimited with //, for example::
 
    notmuch search 'from:"/bob@.*[.]example[.]com/"'