Prevent duplicate attachments

This will prevent users from adding duplicate attachments. This bug surfaced when rendering a mailable for logging or storage before sending.

src/Illuminate/Mail/Mailable.php

@@ -747,7 +747,10 @@ public function with($key, $value = null)
      */
     public function attach($file, array $options = [])
     {
-        $this->attachments[] = compact('file', 'options');
+        $this->attachments = collect($this->attachments)
+                    ->push(compact('file', 'options'))
+                    ->unique('file')
+                    ->all();
 
         return $this;
     }
@@ -776,12 +779,14 @@ public function attachFromStorage($path, $name = null, array $options = [])
      */
     public function attachFromStorageDisk($disk, $path, $name = null, array $options = [])
     {
-        $this->diskAttachments[] = [
+        $this->diskAttachments = collect($this->diskAttachments)->push([
             'disk' => $disk,
             'path' => $path,
             'name' => $name ?? basename($path),
             'options' => $options,
-        ];
+        ])->unique(function ($file) {
+            return $file['disk'].$file['path'];
+        })->all();
 
         return $this;
     }
@@ -796,7 +801,10 @@ public function attachFromStorageDisk($disk, $path, $name = null, array $options
      */
     public function attachData($data, $name, array $options = [])
     {
-        $this->rawAttachments[] = compact('data', 'name', 'options');
+        $this->rawAttachments = collect($this->rawAttachments)
+                ->push(compact('data', 'name', 'options'))
+                ->unique('data')
+                ->all();
 
         return $this;
     }