Tramp code cleanup

* lisp/net/tramp.el (tramp-use-absolute-autoload-file-names)
(tramp-skeleton-file-name-all-completions)
(tramp-parse-auth-sources, tramp-parse-file, tramp-parse-netrc):
* lisp/net/tramp-cache.el (tramp-parse-connection-properties):
* lisp/net/tramp-gvfs.el (tramp-gvfs-parse-device-names):
* lisp/net/tramp-sh.el (tramp-sh-handle-insert-directory):
Use `seq-uniq'.

* lisp/net/tramp.el (tramp-register-foreign-file-name-handler):
* lisp/net/tramp-fuse.el (tramp-fuse-handle-directory-files):
Use `seq-union'.

* test/lisp/net/tramp-archive-tests.el
(tramp-archive-test17-insert-directory):
* test/lisp/net/tramp-tests.el (tramp-test17-insert-directory):
Use `seq-union'.
(tramp-test42-utf8): Use `seq-uniq' and `tramp-compat-seq-keep'.

2 files changed, 5 insertions, 6 deletions

diff --git a/test/lisp/net/tramp-archive-tests.el b/test/lisp/net/tramp-archive-tests.el
index 0ff0f3ddd4d..33dc0b9d4af 100644
--- a/test/lisp/net/tramp-archive-tests.el
+++ b/test/lisp/net/tramp-archive-tests.el
@@ -559,7 +559,7 @@ This checks also `file-name-as-directory', `file-name-directory',
 
   (let (;; We test for the summary line.  Keyword "total" could be localized.
         (process-environment
-         (append '("LANG=C" "LANGUAGE=C" "LC_ALL=C") process-environment)))
+         (seq-union '("LANG=C" "LANGUAGE=C" "LC_ALL=C") process-environment)))
     (unwind-protect
         (progn
           (with-temp-buffer
diff --git a/test/lisp/net/tramp-tests.el b/test/lisp/net/tramp-tests.el
index 7b90bb4d9be..e011b99be57 100644
--- a/test/lisp/net/tramp-tests.el
+++ b/test/lisp/net/tramp-tests.el
@@ -3515,7 +3515,7 @@ This tests also `file-directory-p' and `file-accessible-directory-p'."
            (tmp-name2 (expand-file-name "foo" tmp-name1))
            ;; We test for the summary line.  Keyword "total" could be localized.
            (process-environment
-            (append '("LANG=C" "LANGUAGE=C" "LC_ALL=C") process-environment)))
+            (seq-union '("LANG=C" "LANGUAGE=C" "LC_ALL=C") process-environment)))
       (unwind-protect
           (progn
             (make-directory tmp-name1)
@@ -5656,8 +5656,7 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
 (ert-deftest tramp-test30-make-process ()
   "Check `make-process'."
   :tags (append '(:expensive-test :tramp-asynchronous-processes)
-                (and (getenv "EMACS_EMBA_CI")
-                     '(:unstable)))
+                (and (getenv "EMACS_EMBA_CI") '(:unstable)))
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-supports-processes-p))
 
@@ -7887,8 +7886,8 @@ This requires restrictions of file name syntax."
        "🌈🍒👋")
 
       (when (and (tramp--test-expensive-test-p) (not (tramp--test-windows-nt-p)))
-        (delete-dups
-         (mapcar
+        (seq-uniq
+         (tramp-compat-seq-keep
           ;; Use all available language specific snippets.
           (lambda (x)
             (and