Add logic to be able to override the default desktop on a per-arch basis

Override to xfce for kfreebsd and hurd. This was previously done in several
different places, including debian-cd and d-i boot parameters.

tasksel/desktop no longer has a default value, instead
/usr/lib/tasksel/default_desktop is used to look it up for an architecture.
This shell library might also be used by eg, debian-cd.

(It would also be ok to make tests/default-desktop vary the default based on
eg, machine hardware (ie, for a tablet, or a machine without much ram).)

Makefile

@@ -36,6 +36,7 @@ install:
 		$(DESTDIR)/usr/share/man/man8
 	install -m 755 tasksel.pl $(DESTDIR)/usr/bin/tasksel
 	install -m 755 tasksel-debconf $(DESTDIR)/usr/lib/tasksel/
+	install -m 644 default_desktop $(DESTDIR)/usr/lib/tasksel/
 	install -m 755 tests/new-install $(DESTDIR)/usr/lib/tasksel/tests/
 	install -m 755 tests/debconf $(DESTDIR)/usr/lib/tasksel/tests/
 	install -m 755 tests/lang $(DESTDIR)/usr/lib/tasksel/tests/

debian/changelog

@@ -5,6 +5,11 @@ tasksel (3.27) UNRELEASED; urgency=low
 
   [ Joey Hess ]
   * Add orca to lxde and mate. Closes: #762409, #762408
+  * Add logic to be able to override the default desktop on a per-arch basis,
+    and override to xfce for kfreebsd and hurd. This was previously done in
+    several different places, including debian-cd and d-i boot parameters.
+  * /usr/lib/tasksel/default_desktop is a shell library that debian-cd
+    etc can use if they want to know what tasksel's default is.
 
  -- Cyril Brulebois <kibi@debian.org>  Sat, 20 Sep 2014 17:43:29 +0200
 

debian/templates

@@ -18,9 +18,7 @@ _Description: Choose software to install:
 Template: tasksel/desktop
 Type: multiselect
 Choices: gnome, kde, xfce, lxde, cinnamon, mate
-Default: gnome
-Description: The desktop environment to install when the desktop task is selected
- This can be preseeded to change the default.
+Description: This can be preseeded to override the default desktop.
 
 Template: tasksel/title
 Type: title

default_desktop

@@ -0,0 +1,10 @@
+# shell library to get the default desktop that tasksel will select 
+# for an architecture
+
+default_desktop_for_arch() {
+	case "$1" in
+		kfreebsd-*) echo xfce ;;
+		hurd-*) echo xfce ;;
+		*) echo gnome ;;
+	esac
+}

tests/default-desktop

@@ -1,8 +1,12 @@
 #!/bin/sh
-# Test-default-desktop: 3 gnome
-# Will check if tasksel/desktop has been preseeded to "gnome".
-# If not, exits with the provided value.
-# (3 will display the task not marked for installation).
+# Test-default-desktop: 3 $desktopname
+# 
+# Will check if tasksel/desktop has been preseeded to "$desktopname",
+# or if it's the default desktop for the architecture.
+# If so, marks the task for installation.
+#
+# Otherwise, exits with the provided value.
+# (3 will display the task not marked for installation; ).
 set +e
 
 DEFAULT="$2"
@@ -13,12 +17,21 @@ if ! [ "$NEW_INSTALL" ]; then
 fi
 
 . /usr/share/debconf/confmodule
+. /usr/lib/tasksel/default_desktop
 
-if db_get "tasksel/desktop" && echo "$RET" | grep -q "$DESKTOPNAME"; then
+check_desktop_wanted() {
 	# see if the desktop test thinks the system wants a desktop
 	/usr/lib/tasksel/tests/desktop
 	if [ "$?" = 2 ]; then
 		exit 2
 	fi
+}
+
+if db_get "tasksel/desktop" && echo "$RET" | grep -q "$DESKTOPNAME"; then
+	check_desktop_wanted
+else
+	if [ "$DESKTOPNAME" = "$(default_desktop_for_arch $(dpkg --print-architecture))" ]; then
+		check_desktop_wanted
+	fi
 fi
 exit $DEFAULT