Run 'git fetch' in SeaBIOS only when really needed

This allows coreboot to compile without Internet connectivity

Change-Id: I969471e44e417f127fdc8744e868211500acee3e
Signed-off-by: Cristian Măgherușan-Stanciu <cristi.magherusan@gmail.com>
Reviewed-on: http://review.coreboot.org/11
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

payloads/external/SeaBIOS/Makefile.inc

@@ -5,12 +5,18 @@ TAG-$(CONFIG_SEABIOS_STABLE)=1efb10b9ea30c45a8c9c6230234fefa10d2886ed
 
 unexport KCONFIG_AUTOCONFIG
 
-all: seabios
+all: build
 
-checkout:
-	echo "    GIT        SeaBIOS $(TAG-y)"
-	test -d seabios && ( cd seabios; git fetch ) || \
+seabios:
+	echo "    Cloning SeaBIOS from Git"
 	git clone git://git.seabios.org/seabios.git
+
+fetch: seabios
+	cd seabios; git show $(TAG-y) >/dev/null 2>&1 ;	if [ $$? -ne 0 ]; \
+	then echo "    Fetching new commits from the SeaBIOS git repo"; git fetch; fi
+
+checkout: fetch
+	echo "    Checking out SeaBIOS revision $(TAG-y)"
 	cd seabios; git checkout master; git branch -D coreboot 2>/dev/null; git checkout -b coreboot $(TAG-y)
 
 config: checkout
@@ -25,7 +31,7 @@ config: checkout
 	# This shows how to force a previously set .config option *off*
 	#echo "# CONFIG_SMBIOS is not set" >> seabios/.config
 
-seabios: config
+build: config
 	echo "    MAKE       SeaBIOS $(TAG-y)"
 	$(MAKE) -C seabios
 
@@ -35,4 +41,4 @@ clean:
 distclean:
 	rm -rf seabios
 
-.PHONY: checkout config seabios clean distclean
+.PHONY: checkout config build clean distclean clone fetch