appview: pages/templates: fix up copy

appview/pages/templates/repo/pulls/fragments/pullCompareBranches.html

···
             </select>
         </div>
     </div>
+
+    <p class="mt-4">
+        Title and description are optional; if left out, they will be extracted
+        from the first commit.
+    </p>
 {{ end }}

appview/pages/templates/repo/pulls/fragments/pullCompareForks.html

···
             </div>
         </div>
     </div>
+    <p class="mt-4">
+        Title and description are optional; if left out, they will be extracted
+        from the first commit.
+    </p>
 {{ end }}

appview/state/pull.go

···
 	}
 
 	if patchutil.IsFormatPatch(patch) {
-		s.pages.Notice(w, "patch-preview", "Format patch detected. Title and description are optional; if left out, they will be extracted from the first commit.")
+		s.pages.Notice(w, "patch-preview", "git-format-patch detected. Title and description are optional; if left out, they will be extracted from the first commit.")
 	} else {
-		s.pages.Notice(w, "patch-preview", "Regular diff detected. Please provide a title and description.")
+		s.pages.Notice(w, "patch-preview", "Regular git-diff detected. Please provide a title and description.")
 	}
 }