fix bug in remote TRAMP saving

Have to disable age file handling in TRAMP encoding/decoding contexts
to prevent accidental decrypts when TRAMP encodes the local age file
contents through it's write-region handler.

age.el

@@ -60,6 +60,23 @@
 (require 'rfc6068)
 (eval-when-compile (require 'cl-lib))
 (eval-when-compile (require 'subr-x))
+(eval-when-compile (require 'tramp-sh))
+
+;;; TRAMP handling advice
+
+;;disable age file handlers on local encoding
+(defun age-tramp-sh-handle-write-region-advice (orig-tramp-sh-handle-write-region &rest args)
+  "This advice disables age file handling in TRAMP region writes.
+This prevents TRAMP from triggering age file decryption when inserting local
+copies of the file during its write-region encoding. This is similar to how
+`epa-file-handler' is inhibited, but since we're not part of emacs we have
+to advice TRAMP to ignore `age-file-handler' instead."
+  (cl-letf (((symbol-value 'file-name-handler-alist)
+             (remq age-file-handler file-name-handler-alist))
+            ((symbol-value 'auto-mode-alist)
+             (remq age-file-auto-mode-alist-entry auto-mode-alist)))
+    (apply orig-tramp-sh-handle-write-region args)))
+(advice-add 'tramp-sh-handle-write-region :around #'age-tramp-sh-handle-write-region-advice)
 
 ;;; Configuration