help: load module doc of disabled extension in extensions.disabledcmd()

This helps rewriting _finddisablecmd() to not load the module.

mercurial/extensions.py

@@ -675,11 +675,12 b' def _finddisabledcmd(ui, cmd, name, path'
             break
     else:
         cmd = aliases[0]
-    return (cmd, name, mod)
+    doc = gettext(pycompat.getdoc(mod))
+    return (cmd, name, doc)
 
 def disabledcmd(ui, cmd, strict=False):
     '''import disabled extensions until cmd is found.
-    returns (cmdname, extname, module)'''
+    returns (cmdname, extname, doc)'''
 
     paths = _disabledpaths(strip_init=True)
     if not paths:

mercurial/help.py

@@ -574,9 +574,9 b' def help_(ui, commands, name, unknowncmd'
         return rst
 
     def helpextcmd(name, subtopic=None):
-        cmd, ext, mod = extensions.disabledcmd(ui, name,
+        cmd, ext, doc = extensions.disabledcmd(ui, name,
                                                ui.configbool('ui', 'strict'))
-        doc = gettext(pycompat.getdoc(mod)).splitlines()[0]
+        doc = doc.splitlines()[0]
 
         rst = listexts(_("'%s' is provided by the following "
                               "extension:") % cmd, {ext: doc}, indent=4,