Restrict valid page names

plug-api/lib/page.ts

@@ -1,4 +1,4 @@
 export function isValidPageName(name: string): boolean {
   // Page can not be empty and not end with a file extension (e.g. "bla.md")
-  return name !== "" && !/\.[a-zA-Z]+$/.test(name);
+  return name !== "" && !name.startsWith(".") && !/\.[a-zA-Z]+$/.test(name);
 }

plugs/core/page.ts

@@ -139,7 +139,7 @@ export async function renamePage(cmdDef: any) {
 
   if (!isValidPageName(newName)) {
     return editor.flashNotification(
-      "Invalid page name: page names cannot end with a file extension",
+      "Invalid page name: page names cannot end with a file extension nor start with a '.'",
       "error",
     );
   }

plugs/markdown/markdown_render.ts

@@ -394,8 +394,8 @@ export function renderMarkdownToHtml(
         t.attrs!.src = options.translateUrls!(t.attrs!.src!);
       }
 
-      if (t.name === "a") {
+      if (t.name === "a" && t.attrs!.href) {
-        t.attrs!.href = options.translateUrls!(t.attrs!.href!);
+        t.attrs!.href = options.translateUrls!(t.attrs!.href);
       }
     });
   }

web/editor.tsx

@@ -1167,7 +1167,7 @@ export class Editor {
 
     if (!isValidPageName(name)) {
       return this.flashNotification(
-        "Invalid page name: page names cannot end with a file extension",
+        "Invalid page name: page names cannot end with a file extension nor start with a '.'",
         "error",
       );
     }