+for (qw[make(1) flock(2) setrlimit(2) vfork(2) tmpfs(5) inotify(7) unix(7)
+ syslog(3)]) {
+ my ($n, $s) = (/([\w\-]+)\((\d)\)/);
+ $xurls{$_} = "https://www.man7.org/linux/man-pages/man$s/$n.$s.html";
+}
+
+for (qw[git(1)
+ git-am(1)
+ git-apply(1)
+ git-config(1)
+ git-credential(1)
+ git-daemon(1)
+ git-diff(1)
+ git-fast-import(1)
+ git-fetch(1)
+ git-filter-branch(1)
+ git-format-patch(1)
+ git-gc(1)
+ git-http-backend(1)
+ git-imap-send(1)
+ git-init(1)
+ git-send-email(1)
+ gitrepository-layout(5)
+ gitglossary(7)
+]) {
+ my ($n) = (/([\w\-\.]+)/);
+ $xurls{$_} = "https://kernel.org/pub/software/scm/git/docs/$n.html"
+}
+
+for (qw[
+ sd_listen_fds(3)
+ systemd(1)
+ systemd.unit(5)
+ systemd.socket(5)
+]) {
+ my ($n) = (/([\w\-\.]+)/);
+ $xurls{$_} = "https://www.freedesktop.org/software/systemd/man/$n.html";
+}
+
+# favor upstream docs if they exist, use manpages.debian.org if they don't
+$xurls{'netrc(5)'} = 'https://manpages.debian.org/stable/ftp/netrc.5.en.html';
+$xurls{'mbsync(1)'} =
+ 'https://manpages.debian.org/stable/isync/mbsync.1.en.html';
+$xurls{'offlineimap(1)'} =
+ 'https://manpages.debian.org/stable/offlineimap/offlineimap.1.en.html';
+$xurls{'spamc(1)'} =
+ 'https://spamassassin.apache.org/full/3.4.x/doc/spamc.html';
+$xurls{'grok-pull'} =
+ 'https://git.kernel.org/pub/scm/utils/grokmirror/grokmirror.git' .
+ '/tree/man/grok-pull.1.rst';
+$xurls{'git-filter-repo(1)'} = 'https://github.com/newren/git-filter-repo'.
+ '/blob/master/Documentation/git-filter-repo.txt';
+$xurls{'ssoma(1)'} = 'https://ssoma.public-inbox.org/ssoma.txt';
+$xurls{'cgitrc(5)'} = 'https://git.zx2c4.com/cgit/tree/cgitrc.5.txt';
+$xurls{'prove(1)'} = 'https://perldoc.perl.org/prove.html';
+$xurls{'mbox(5)'} = 'https://manpages.debian.org/stable/mutt/mbox.5.en.html';
+$xurls{'mmdf(5)'} = 'https://manpages.debian.org/stable/mutt/mmdf.5.en.html';
+$xurls{'mutt(1)'} = 'https://manpages.debian.org/stable/mutt/mutt.1.en.html';
+$xurls{'torsocks(1)'} =
+ 'https://manpages.debian.org/stable/torsocks/torsocks.1.en.html';
+$xurls{'curl(1)'} = 'https://manpages.debian.org/stable/curl/curl.1.en.html';
+$xurls{'copydatabase(1)'} =
+ 'https://manpages.debian.org/stable/xapian-tools/copydatabase.1.en.html';
+$xurls{'xapian-compact(1)'} =
+ 'https://manpages.debian.org/stable/xapian-tools/xapian-compact.1.en.html';
+$xurls{'gzip(1)'} = 'https://manpages.debian.org/stable/gzip/gzip.1.en.html';
+$xurls{'chmod(1)'} =
+ 'https://manpages.debian.org/stable/coreutils/chmod.1.en.html';
+$xurls{'kqueue(2)'} =
+ 'https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2';
+$xurls{'notmuch(1)'} = 'https://notmuchmail.org/manpages/notmuch-1/';
+$xurls{'mairix(1)'} =
+ 'https://manpages.debian.org/stable/mairix/mairix.1.en.html';
+
+my $str = do { local $/; <STDIN> };
+my ($title) = ($str =~ /\A([^\n]+)/);
+if ($str =~ /^NAME\n\s+([^\n]+)/sm) {
+ # don't link to ourselves
+ $title = $1;
+ if ($title =~ /([\w\.\-]+)/) {
+ delete $xurls{$1};
+ }
+}