elisp-1.0: load port autoloads via a site-start.d snippet

_resources/port1.0/group/elisp-1.0.tcl

@@ -99,6 +99,13 @@ default elisp.byte_compile  yes
 options elisp.autoloads
 default elisp.autoloads     yes
 
+# Filename prefix for the site-start.d snippet that loads this port's
+# autoloads. Snippets are loaded in lexical filename order; the value is
+# zero-padded so lower numbers load earlier. The default suits ports with no
+# ordering requirements.
+options elisp.site_start_priority
+default elisp.site_start_priority   50
+
 # Internal flag tracking whether a port has opted in to the managed phases.
 set elisp_managed           0
 
@@ -160,14 +167,37 @@ proc elisp.setup {} {
             }
         }
 
-        # Install autoloads file if generated
+        # Install autoloads file if generated, plus a site-start.d snippet so
+        # the emacs port's site-start.el loads it at startup (giving real
+        # autoloading without the user editing their init file).
         set autoload_file "${srcdir}/${pkg}-autoloads.el"
-        if {[file exists $autoload_file]} {
+        if {[option elisp.autoloads] && [file exists $autoload_file]} {
             xinstall -m 0644 $autoload_file ${dest}
+            elisp.install_site_start_snippet ${destroot} ${pkg} ${pkg}-autoloads
         }
     }
 }
 
+# Helper: install a site-start.d snippet that loads ${loaddefs} (an autoloads
+# or loaddefs file, named without the .el suffix) from the port's site-lisp
+# subdirectory, so the emacs port's site-start.el loads it at startup. Exposed
+# so ports that override the managed destroot (e.g. org-mode) can install a
+# snippet themselves.
+proc elisp.install_site_start_snippet {destroot pkg loaddefs} {
+    global emacs_lispdir
+    set ssd ${destroot}${emacs_lispdir}/site-start.d
+    xinstall -d ${ssd}
+    set prio [format %03d [option elisp.site_start_priority]]
+    set snippet ${ssd}/${prio}-${pkg}.el
+    set fh [open ${snippet} w]
+    puts $fh ";; -*- lexical-binding: t; -*-"
+    puts $fh ";; Auto-generated by the elisp 1.0 portgroup for ${pkg}."
+    puts $fh "(add-to-list 'load-path \"${emacs_lispdir}/${pkg}\")"
+    puts $fh "(load \"${emacs_lispdir}/${pkg}/${loaddefs}\" nil t)"
+    close $fh
+    file attributes ${snippet} -permissions 0644
+}
+
 # Helper: resolve the effective list of .el files.
 proc elisp._get_files {} {
     set files [option elisp.files]