Add file name handler support for 'make-process' (Bug#28691)

* src/process.c (Fmake_process): Add new keyword argument
':file-handler'.
(syms_of_process) <make-process, :file-handler>: Define new symbols.

* lisp/files.el (file-name-non-special): Add support for
'make-process'.

* test/src/process-tests.el (make-process/file-handler/found)
(make-process/file-handler/not-found)
(make-process/file-handler/disable): New unit tests.
(process-tests--file-handler): New helper function.

* test/lisp/files-tests.el
(files-tests-file-name-non-special-make-process): New unit test.

* doc/lispref/files.texi (Magic File Names): Document that
'make-process' can invoke file name handlers.

* doc/lispref/processes.texi (Asynchronous Processes): Document
':file-handlers' argument to 'make-process'.

* etc/NEWS (Lisp Changes in Emacs 27.1): Mention new
:file-handler argument for 'make-process'.

1 files changed, 9 insertions, 2 deletions

diff --git a/lisp/files.el b/lisp/files.el
index fb6cf0193a9..448df62710c 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -7103,7 +7103,8 @@ only these files will be asked to be saved."
         (default-directory
           (if (memq operation
                     '(insert-directory process-file start-file-process
-                                       shell-command temporary-file-directory))
+                                       make-process shell-command
+                                       temporary-file-directory))
               (directory-file-name
                (expand-file-name
                 (unhandled-file-name-directory default-directory)))
@@ -7151,7 +7152,13 @@ only these files will be asked to be saved."
                           ;; These file-notify-* operations take a
                           ;; descriptor.
                           (file-notify-rm-watch)
-                          (file-notify-valid-p)))
+                          (file-notify-valid-p)
+                          ;; `make-process' uses keyword arguments and
+                          ;; doesn't mangle its filenames in any way.
+                          ;; It already strips /: from the binary
+                          ;; filename, so we don't have to do this
+                          ;; here.
+                          (make-process)))
                   ;; For all other operations, treat the first
                   ;; argument only as the file name.
                   '(nil 0))))