Add new user option Man-prefer-synchronous-call

* lisp/man.el (Man-getpage-in-background): Add new defcustom
Man-prefer-synchronous-call and modify #'Man-getpage-in-background.
Only call #'start-process when 'make-process satisfies #'fboundp AND
Man-prefer-synchronous-call is bound to nil.  (Bug#61552)

Copyright-paperwork-exempt: yes

doc/emacs/programs.texi

@@ -1387,6 +1387,12 @@ this, change the value of the variable @code{Man-switches} to
 @kbd{M-p} to switch between man pages in different sections.  The mode
 line shows how many manual pages are available.
 
+@vindex Man-prefer-synchronous-call
+  By default, @kbd{M-x man} calls the @code{man} program
+asynchronously.  If you would prefer it if @kbd{M-x man} called the
+@code{man} program synchronously, you may set variable
+@code{Man-prefer-synchronous-calls} to a non-@code{nil} value.
+
 @findex woman
 @cindex manual pages, on MS-DOS/MS-Windows
   An alternative way of reading manual pages is the @kbd{M-x woman}

etc/NEWS

@@ -201,6 +201,13 @@ This command adds a docstring comment to the current defun.  If a
 comment already exists, point is only moved to the comment.  It is
 bound to 'C-c C-d' in 'go-ts-mode'.
 
+** Man-mode
+
++++
+*** New user option 'Man-prefer-synchronous-call'.
+When this is non-nil, call the 'man' program synchronously rather than
+asynchronously, which is the default behaviour.
+
 
 * New Modes and Packages in Emacs 30.1
 

lisp/man.el

@@ -97,6 +97,14 @@
   :group 'external
   :group 'help)
 
+(defcustom Man-prefer-synchronous-call nil
+  "Whether to call the Un*x 'man' program synchronously.
+When this is non-nil, call the 'man' program synchronously
+(rather than asynchronously, which is the default behaviour)."
+  :type 'boolean
+  :group 'man
+  :version 30.1)
+
 (defcustom Man-filter-list nil
   "Manpage cleaning filter command phrases.
 This variable contains a list of the following form:
@@ -1118,7 +1126,8 @@ Return the buffer in which the manpage will appear."
 					"[cleaning...]")
 				      'face 'mode-line-emphasis)))
 	(Man-start-calling
-	 (if (fboundp 'make-process)
+	 (if (and (fboundp 'make-process)
+                  (not Man-prefer-synchronous-call))
 	     (let ((proc (start-process
 			  manual-program buffer
 			  (if (memq system-type '(cygwin windows-nt))