ifeq ($(OS),Windows_NT)
GIT=C:\\Program Files (x86)\\Git\\bin\\git.exe
ifeq ($(shell $(GIT) version),)
GIT=C:\\Program Files\\Git\\bin\\git.exe
ifeq ($(shell $(GIT) version),)
GIT=git.exe
endif
endif
else # UNIX
GIT=git
endif

VERSION:=$(shell "$(GIT)" describe)
VERSION:=$(if $(VERSION),$(VERSION),unknown)

ifneq ($(VERSION),unknown)
# Always update version.h if we are in a git repo. Otherwise create
# the file only if it does not exist.
.PHONY: version.h
endif

version.h:
ifeq ($(OS),Windows_NT)
	echo #define GIT_VERSION "$(VERSION)" > $@
else
	echo '#define GIT_VERSION "$(VERSION)"' > $@
endif