Rename internal--external-sockname and document (Bug#24218)

* lisp/server.el: Rename `internal--external-sockname' to
  `internal-daemon-sockname'.
* src/process.c: Likewise.
* doc/lispref/processes.texi: Document `internal-daemon-sockname'.

doc/lispref/processes.texi

@@ -2862,9 +2862,9 @@ non-@code{nil} if that particular network option is supported by
 @node Misc Network
 @section Misc Network Facilities
 
-  These additional functions are useful for creating and operating
-on network connections.  Note that they are supported only on some
-systems.
+  These additional functions and variables are useful for creating and
+operating on network connections.  Note that they are supported only
+on some systems.
 
 @defun network-interface-list
 This function returns a list describing the network interfaces
@@ -2913,6 +2913,17 @@ If the vector does not include the port number, @var{p}, or if
 @code{:@var{p}} suffix.
 @end defun
 
+@defvar internal--daemon-sockname
+This variable is set to the full path of the socket that has been
+passed to Emacs during socket activation.  This is then used to update
+the @code{server-name} and @code{server-socket-dir} variables to
+reflect the name and path of the socket that was used to launch the
+Emacs daemon process.
+
+If Emacs wasn't started with socket activation, the value of this
+variable is @code{nil}.
+@end defvar
+
 @node Serial Ports
 @section Communicating with Serial Ports
 @cindex @file{/dev/tty}

lisp/server.el

@@ -258,8 +258,8 @@ prevents multiple initializations when an external socket has
 been consumed.")
 
 (defcustom server-name
-  (if internal--external-sockname
-      (file-name-nondirectory internal--external-sockname)
+  (if internal-daemon-sockname
+      (file-name-nondirectory internal-daemon-sockname)
     "server")
   "The name of the Emacs server, if this Emacs process creates one.
 The command `server-start' makes use of this.  It should not be
@@ -271,8 +271,8 @@ changed while a server is running."
 ;; We do not use `temporary-file-directory' here, because emacsclient
 ;; does not read the init file.
 (defvar server-socket-dir
-  (if internal--external-sockname
-      (file-name-directory internal--external-sockname)
+  (if internal-daemon-sockname
+      (file-name-directory internal-daemon-sockname)
     (and (featurep 'make-network-process '(:family local))
          (format "%s/emacs%d" (or (getenv "TMPDIR") "/tmp") (user-uid))))
   "The directory in which to place the server socket.
@@ -631,7 +631,7 @@ To force-start a server, do \\[server-force-delete] and then
       ;; Check to see if an uninitialized external socket has been
       ;; passed in, if that is the case, skip checking
       ;; `server-running-p' as this will return the wrong result.
-      (if (and internal--external-sockname
+      (if (and internal-daemon-sockname
                (not server--external-socket-initialized))
           (setq server--external-socket-initialized t)
         ;; Delete the socket files made by previous server invocations.

src/process.c

@@ -8023,7 +8023,7 @@ init_process_emacs (int sockfd)
 	sockname = conv_sockaddr_to_lisp (&sa.sa, salen);
     }
 # endif
-  Vinternal__external_sockname = sockname;
+  Vinternal_daemon_sockname = sockname;
 
   max_desc = -1;
   memset (fd_callback_info, 0, sizeof (fd_callback_info));
@@ -8217,9 +8217,9 @@ These functions are called in the order of the list, until one of them
 returns non-`nil'.  */);
   Vinterrupt_process_functions = list1 (Qinternal_default_interrupt_process);
 
-  DEFVAR_LISP ("internal--external-sockname", Vinternal__external_sockname,
+  DEFVAR_LISP ("internal-daemon-sockname", Vinternal_daemon_sockname,
 	       doc: /* Name of external socket passed to Emacs, or nil if none.  */);
-  Vinternal__external_sockname = Qnil;
+  Vinternal_daemon_sockname = Qnil;
 
   DEFSYM (Qinternal_default_interrupt_process,
 	  "internal-default-interrupt-process");