Fix copy-directory bug when dest dir exists

* lisp/files.el (copy-directory): Set ‘follow’ depending on
whether we made the directory, not based on a guess that is
sometimes wrong.  When NEWNAME is a directory name and
COPY-CONTENTS is nil, do not object merely because the adjusted
NEWNAME is already a directory.  (Bug#58919).
* test/lisp/files-tests.el (files-tests-copy-directory):
Test for the bug.

1 files changed, 8 insertions, 1 deletions

diff --git a/test/lisp/files-tests.el b/test/lisp/files-tests.el
index b9fbeb8a4e0..011bfa67cc2 100644
--- a/test/lisp/files-tests.el
+++ b/test/lisp/files-tests.el
@@ -1346,7 +1346,9 @@ name (Bug#28412)."
            (dest (concat dirname "dest/new/directory/"))
            (file (concat (file-name-as-directory source) "file"))
            (source2 (concat dirname "source2"))
-           (dest2 (concat dirname "dest/new2")))
+           (dest2 (concat dirname "dest/new2"))
+           (source3 (concat dirname "source3/d"))
+           (dest3 (concat dirname "dest3/d")))
       (make-directory source)
       (write-region "" nil file)
       (copy-directory source dest t t t)
@@ -1354,6 +1356,11 @@ name (Bug#28412)."
       (make-directory (concat (file-name-as-directory source2) "a") t)
       (copy-directory source2 dest2)
       (should (file-directory-p (concat (file-name-as-directory dest2) "a")))
+      (make-directory source3 t)
+      (write-region "x\n" nil (concat (file-name-as-directory source3) "file"))
+      (make-directory dest3 t)
+      (write-region "y\n" nil (concat (file-name-as-directory dest3) "file"))
+      (copy-directory source3 (file-name-directory dest3) t)
       (delete-directory dir 'recursive))))
 
 (ert-deftest files-tests-abbreviate-file-name-homedir ()