appview/repo: add an option to choose the name of the forked repo

Given that repo names cannot be changed later, this gives the
freedom to choose the name and still stay in the fork network.

Signed-off-by: Vidya Sagar VOBBILISETTI <[e-mail]>

appview/pages/templates/repo/fork.html

···
 </div>
 <div class="p-6 bg-white dark:bg-gray-800 drop-shadow-sm rounded">
   <form hx-post="/{{ .RepoInfo.FullName }}/fork" class="space-y-12" hx-swap="none" hx-indicator="#spinner">
+
+    <fieldset class="space-y-3">
+      <legend for="repo_name" class="dark:text-white">Repository name</legend>
+      <input type="text" id="repo_name" name="repo_name" value="{{ .RepoInfo.Name }}"
+        class="w-full p-2 border rounded bg-gray-100 dark:bg-gray-700 dark:text-white dark:border-gray-600" />
+    </fieldset>
+
     <fieldset class="space-y-3">
       <legend class="dark:text-white">Select a knot to fork into</legend>
       <div class="space-y-2">

appview/repo/repo.go

···
 		}
 
 		// choose a name for a fork
-		forkName := f.Name
+		forkName := r.FormValue("repo_name")
+		if forkName == "" {
+			rp.pages.Notice(w, "repo", "Repository name cannot be empty.")
+			return
+		}
+
 		// this check is *only* to see if the forked repo name already exists
 		// in the user's account.
 		existingRepo, err := db.GetRepo(
 			rp.db,
 			db.FilterEq("did", user.Did),
-			db.FilterEq("name", f.Name),
+			db.FilterEq("name", forkName),
 		)
 		if err != nil {
-			if errors.Is(err, sql.ErrNoRows) {
-				// no existing repo with this name found, we can use the name as is
-			} else {
+			if !errors.Is(err, sql.ErrNoRows) {
 				log.Println("error fetching existing repo from db", "err", err)
 				rp.pages.Notice(w, "repo", "Failed to fork this repository. Try again later.")
 				return
 			}
 		} else if existingRepo != nil {
-			// repo with this name already exists, append random string
-			forkName = fmt.Sprintf("%s-%s", forkName, randomString(3))
+			// repo with this name already exists
+			rp.pages.Notice(w, "repo", "A repository with this name already exists.")
+			return
 		}
 		l = l.With("forkName", forkName)