Add a direntry to the Rottlog info manual.

diff --git a/doc/rottlog.texi b/doc/rottlog.texi
index 0ba8019..0f29916 100644
--- a/doc/rottlog.texi
+++ b/doc/rottlog.texi
@@ -18,6 +18,11 @@ Documentation License.''
 @end quotation
 @end copying
 
+@dircategory System administration
+@direntry
+* Rottlog: (rottlog).         The GNU log management utility.
+@end direntry
+
 @paragraphindent none
 
 @iftex
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<div class='path'>path: <a href='/guix/log/?id=dd63cd7876f8c6a6eb42170219c17659ff4daf42'>root</a>/<a href='/guix/log/tests?id=dd63cd7876f8c6a6eb42170219c17659ff4daf42'>tests</a>/<a href='/guix/log/tests/substitute.scm?id=dd63cd7876f8c6a6eb42170219c17659ff4daf42'>substitute.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/substitute.scm?id=dd63cd7876f8c6a6eb42170219c17659ff4daf42&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-12-04 22:26:36 +0100'>2023-12-04</span></td><td><a href='/guix/commit/tests/substitute.scm?id=06b9c1260c72935806957bf302c40c1db6101a63'>substitute: Do not exit when failing to find a nar.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://issues.guix.gnu.org/67575&gt;.

* guix/scripts/substitute.scm (process-substitution/fallback): Use
‘report-error’ instead of ‘leave’.  Write status line to PORT.
* tests/substitute.scm ("substitute, narinfo is available but nar is
missing"): Adjust accordingly.

Change-Id: Ic7297dbd563c007111ec2167c8d52505a07d4822
</span></span></td><td>Ludovic Courtès</td></tr>