package/skeleton: make it a virtual package

We now have two packages that can act as a skeleton, skeleton-common,
also known as our default skeleton, and skeleton-custom.

This means that the skeleton package can be a standard virtual package
now.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/skeleton-common/Config.in

@@ -1,3 +1,6 @@
 config BR2_PACKAGE_SKELETON_COMMON
 	bool
-	select BR2_PACKAGE_SKELETON
+	select BR2_PACKAGE_HAS_SKELETON
+
+config BR2_PACKAGE_PROVIDES_SKELETON
+	default "skeleton-common" if BR2_PACKAGE_SKELETON_COMMON

package/skeleton-common/skeleton-common.mk

@@ -11,6 +11,8 @@
 SKELETON_COMMON_ADD_TOOLCHAIN_DEPENDENCY = NO
 SKELETON_COMMON_ADD_SKELETON_DEPENDENCY = NO
 
+SKELETON_COMMON_PROVIDES = skeleton
+
 # The skeleton also handles the merged /usr case in the sysroot
 SKELETON_COMMON_INSTALL_STAGING = YES
 

package/skeleton-custom/Config.in

@@ -1,3 +1,6 @@
 config BR2_PACKAGE_SKELETON_CUSTOM
 	bool
-	select BR2_PACKAGE_SKELETON
+	select BR2_PACKAGE_HAS_SKELETON
+
+config BR2_PACKAGE_PROVIDES_SKELETON
+	default "skeleton-custom" if BR2_PACKAGE_SKELETON_CUSTOM

package/skeleton-custom/skeleton-custom.mk

@@ -11,7 +11,8 @@
 SKELETON_CUSTOM_ADD_TOOLCHAIN_DEPENDENCY = NO
 SKELETON_CUSTOM_ADD_SKELETON_DEPENDENCY = NO
 
-# The skeleton also handles the merged /usr case in the sysroot
+SKELETON_CUSTOM_PROVIDES = skeleton
+
 SKELETON_CUSTOM_INSTALL_STAGING = YES
 
 SKELETON_CUSTOM_PATH = $(call qstrip,$(BR2_ROOTFS_SKELETON_CUSTOM_PATH))

package/skeleton/Config.in

@@ -1,4 +1,9 @@
 config BR2_PACKAGE_SKELETON
 	bool
-	help
-	  The basic skeleton for your rootfs.
+	default y
+
+config BR2_PACKAGE_HAS_SKELETON
+	bool
+
+config BR2_PACKAGE_PROVIDES_SKELETON
+	string

package/skeleton/skeleton.mk

@@ -11,10 +11,4 @@
 SKELETON_ADD_TOOLCHAIN_DEPENDENCY = NO
 SKELETON_ADD_SKELETON_DEPENDENCY = NO
 
-ifeq ($(BR2_PACKAGE_SKELETON_CUSTOM),y)
-SKELETON_DEPENDENCIES = skeleton-custom
-else
-SKELETON_DEPENDENCIES = skeleton-common
-endif
-
-$(eval $(generic-package))
+$(eval $(virtual-package))

system/Config.in

@@ -1,5 +1,9 @@
 menu "System configuration"
 
+# Note: usually, it is not possible to select a provider of a virtual
+# package. But here we have an exception: there are only two providers
+# and they only get selected each by separate entries in this choice.
+# So this is a safe situation.
 choice
 	prompt "Root FS skeleton"