lib-storage: Add MAILBOX_FLAG_FSCK to fsck index immediately after op…

…ening it

This can be used to fix a broken index that is causing mailbox_open() to
fail.

src/lib-storage/index/index-storage.c

@@ -332,6 +332,12 @@ int index_storage_mailbox_open(struct mailbox *box, bool move_to_memory)
 			return -1;
 		}
 	}
+	if ((box->flags & MAILBOX_FLAG_FSCK) != 0) {
+		if (mail_index_fsck(box->index) < 0) {
+			mailbox_set_index_error(box);
+			return -1;
+		}
+	}
 
 	box->cache = mail_index_get_cache(box->index);
 	index_cache_register_defaults(box);

src/lib-storage/mail-storage.h

@@ -68,7 +68,11 @@ enum mailbox_flags {
 	/* Mailbox is created implicitly if it does not exist. */
 	MAILBOX_FLAG_AUTO_CREATE	= 0x1000,
 	/* Mailbox is subscribed to implicitly when it is created automatically */
-	MAILBOX_FLAG_AUTO_SUBSCRIBE	= 0x2000
+	MAILBOX_FLAG_AUTO_SUBSCRIBE	= 0x2000,
+	/* Run fsck for mailbox index before doing anything else. This may be
+	   useful in fixing index corruption errors that aren't otherwise
+	   detected and that are causing the full mailbox opening to fail. */
+	MAILBOX_FLAG_FSCK		= 0x4000,
 };
 
 enum mailbox_feature {