[source] base-files: add support for overlaying rootfs content

[LEDE Commits]

blogic pushed a commit to source.git, branch master:
https://git.lede-project.org/b5222924059f5146007a02e33d317f2c04d7dd0b

commit b5222924059f5146007a02e33d317f2c04d7dd0b
Author: Rafał Miłecki <rafal at milecki.pl>
AuthorDate: Wed Dec 7 16:19:08 2016 +0100

    base-files: add support for overlaying rootfs content
    
    This adds support for install-overlay define. When used in package it
    allows installing files to a special directory that gets copied to the
    root when installing it.
    It allows overwriting files provided by other packages.
    
    Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
 include/package-ipkg.mk                   | 9 +++++++++
 package/base-files/files/lib/functions.sh | 5 +++++
 2 files changed, 14 insertions(+)

diff --git a/include/package-ipkg.mk b/include/package-ipkg.mk
index afd2d4e..e168eb3 100644
--- a/include/package-ipkg.mk
+++ b/include/package-ipkg.mk
@@ -96,7 +96,14 @@ ifeq ($(DUMP),)
     KEEP_$(1):=$(strip $(call Package/$(1)/conffiles))
 
     ifeq ($(BUILD_VARIANT),$$(if $$(VARIANT),$$(VARIANT),$(BUILD_VARIANT)))
+    do_install=
     ifdef Package/$(1)/install
+      do_install=yes
+    endif
+    ifdef Package/$(1)/install-overlay
+      do_install=yes
+    endif
+    ifdef do_install
       ifneq ($(CONFIG_PACKAGE_$(1))$(DEVELOPER),)
         IPKGS += $(1)
         compile: $$(IPKG_$(1)) $(PKG_INFO_DIR)/$(1).provides $(STAGING_DIR_ROOT)/stamp/.$(1)_installed
@@ -178,6 +185,8 @@ $(_endef)
 	@rm -rf $$(IDIR_$(1)) $$(call opkg_package_files,$(1))
 	mkdir -p $(PACKAGE_DIR) $$(IDIR_$(1))/CONTROL $(PKG_INFO_DIR)
 	$(call Package/$(1)/install,$$(IDIR_$(1)))
+	$(if $(Package/$(1)/install-overlay),mkdir -p $(PACKAGE_DIR) $$(IDIR_$(1))/rootfs-overlay)
+	$(call Package/$(1)/install-overlay,$$(IDIR_$(1))/rootfs-overlay)
 	-find $$(IDIR_$(1)) -name 'CVS' -o -name '.svn' -o -name '.#*' -o -name '*~'| $(XARGS) rm -rf
 	@( \
 		find $$(IDIR_$(1)) -name lib\*.so\* -or -name \*.ko | awk -F/ '{ print $$$$NF }'; \
diff --git a/package/base-files/files/lib/functions.sh b/package/base-files/files/lib/functions.sh
index b3bf221..b68db6b 100755
--- a/package/base-files/files/lib/functions.sh
+++ b/package/base-files/files/lib/functions.sh
@@ -230,6 +230,11 @@ default_postinst() {
 		ret=$?
 	fi
 
+	if [ -d "$root/rootfs-overlay" ]; then
+		cp -R $root/rootfs-overlay/. $root/
+		rm -fR $root/rootfs-overlay/
+	fi
+
 	if [ -z "$root" ] && grep -q -s "^/etc/uci-defaults/" "/usr/lib/opkg/info/${pkgname}.list"; then
 		. /lib/functions/system.sh
 		[ -d /tmp/.uci ] || mkdir -p /tmp/.uci