fix handling of maxKeys in SearchKey

changelog/unreleased/pull-3776

@@ -0,0 +1,10 @@
+Bugfix: Limit number of key files tested while opening a repository
+
+Previously, restic tested the password against every key in the repository, when
+there are more and more keys in the repository, opening the repository becomes
+slower and slower.
+
+Now restic tests password up to 20 times on the key file in the repository, or
+you can use `-key-hint=<Key ID>` to specify the key file to be used.
+
+https://github.com/restic/restic/pull/3776

internal/repository/key.go

@@ -137,6 +137,7 @@ func SearchKey(ctx context.Context, s *Repository, password string, maxKeys int,
 
 	// try at most maxKeys keys in repo
 	err = s.Backend().List(listCtx, restic.KeyFile, func(fi restic.FileInfo) error {
+		checked++
 		if maxKeys > 0 && checked > maxKeys {
 			return ErrMaxKeysReached
 		}