Rename "search path" to "library roots"

* lisp/emacs-lisp/cl-seq.el (cl-set-difference): Retain the order
of the elements from CL-LIST1.

* test/automated/cl-lib-tests.el (cl-lib-test-set-functions):
Update WRT to the above change.

* lisp/progmodes/project.el (project-search-path-function): Rename
to project-library-roots-function, update the documentation and
references.
(project-search-path): Likewise, to project-library-roots.
(project-roots): Clarify documentation.
(project-vc-search-path): Likewise, to project-vc-library-roots.
(project-library-roots): In addition to the renames, thread the
results through file-name-as-directory.
(project-prune-directories): Accept a variable number of
arguments.  Rename to project-combine-directories.
(project-subtract-directories): New function.

* lisp/progmodes/elisp-mode.el (elisp--xref-find-references):
Append project-roots and project-library-roots together.

* lisp/progmodes/etags.el (etags--xref-find-references): Ditto.

1 files changed, 1 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/cl-seq.el b/lisp/emacs-lisp/cl-seq.el
index 3aea67ad11b..5f0f0881210 100644
--- a/lisp/emacs-lisp/cl-seq.el
+++ b/lisp/emacs-lisp/cl-seq.el
@@ -849,7 +849,7 @@ to avoid corrupting the original LIST1 and LIST2.
 		(memq (car cl-list1) cl-list2))
 	      (push (car cl-list1) cl-res))
 	  (pop cl-list1))
-	cl-res))))
+        (nreverse cl-res)))))
 
 ;;;###autoload
 (defun cl-nset-difference (cl-list1 cl-list2 &rest cl-keys)