generate EXTRAVERSION out of 'git describe ...'

Makefile.defs

@@ -3,13 +3,27 @@ else
 makefile_defs=1
 export makefile_defs
 
-SVN_REV?=r$(shell svnversion -n .)
+GIT = $(shell which git)
+SVNVERSION = $(shell which svnversion)
+
+ifneq ($(GIT),)
+   SCM_REV = $(shell git describe --always --dirty)
+endif
+
+ifeq ($(SCM_REV),)
+ifneq ($(SVNVERSION),)
+   SCM_REV = r$(shell svnversion -n .)
+endif
+endif
 
 #version number
 VERSION = 1
 PATCHLEVEL = 3
 SUBLEVEL = 0
-EXTRAVERSION ?= -dev-$(SVN_REV)
+
+ifneq ($(SCM_REV),)
+EXTRAVERSION = -dev-$(SCM_REV)
+endif
 
 REL_VERSION=$(VERSION).$(PATCHLEVEL).$(SUBLEVEL)
 RELEASE=$(REL_VERSION)$(EXTRAVERSION)