help: list deprecated and experimental extensions if --verbose

This is common in the other help topics.

mercurial/help.py

@@ -62,7 +62,8 b' def extshelp(ui):'
     rst = loaddoc('extensions')(ui).splitlines(True)
     rst.extend(listexts(
         _('enabled extensions:'), extensions.enabled(), showdeprecated=True))
-    rst.extend(listexts(_('disabled extensions:'), extensions.disabled()))
+    rst.extend(listexts(_('disabled extensions:'), extensions.disabled(),
+                        showdeprecated=ui.verbose))
     doc = ''.join(rst)
     return doc
 

tests/test-help.t

@@ -283,6 +283,11 b' Test extension help:'
        win32mbcs     allow the use of MBCS paths with problematic encodings
        zeroconf      discover and advertise repositories on the local network
 
+Verify that deprecated extensions are included if --verbose:
+
+  $ hg -v help extensions | grep children
+       children      command to display child changesets (DEPRECATED)
+
 Verify that extension keywords appear in help templates
 
   $ hg help --config extensions.transplant= templating|grep transplant > /dev/null