ikiwiki: Add help text about name restriction

CHANGELOG.md

@@ -43,6 +43,7 @@ All notable changes to this project will be documented in this file.
   requiring root permission.
 - xmpp: Replace jwchat with jsxc. Bump module version number so
   current installs can be updated.
+- ikiwiki: Allow only alphanumerics in wiki/blog name.
 
 ### Removed
 - Remove width management for forms.

plinth/modules/ikiwiki/forms.py

@@ -30,8 +30,10 @@ class IkiwikiCreateForm(forms.Form):
         label=_('Type'),
         choices=[('wiki', 'Wiki'), ('blog', 'Blog')])
 
-    name = forms.CharField(label=_('Name'),
-                           validators=[RegexValidator(regex='^[a-zA-Z0-9]+$')])
+    name = forms.CharField(
+        label=_('Name'),
+        help_text=_('Only alphanumeric characters are allowed.'),
+        validators=[RegexValidator(regex='^[a-zA-Z0-9]+$')])
 
     admin_name = forms.CharField(label=_('Admin Account Name'))