improve makefile

 o  add 'install' target
 o  shorten the name of INCLUDE_PATHS to IMPORTS
 o  use filename prerequisities and targets rather than phony keywords
 o  add a dependency on .git/refs/tags for the githash target
 o  add githash.txt and dfmt-test to the clean target
 o  add more targets to .PHONY

makefile

@@ -1,33 +1,39 @@
+PREFIX = /usr/local
+
 SRC := $(shell find src -name "*.d") \
 	$(shell find libdparse/src -name "*.d") \
 	$(shell find stdx-allocator/source -name "*.d")
-INCLUDE_PATHS := -Ilibdparse/src -Istdx-allocator/source -Isrc -Jbin
-DMD_COMMON_FLAGS := -dip25 -w $(INCLUDE_PATHS)
+IMPORTS := -Ilibdparse/src -Istdx-allocator/source -Isrc -Jbin
+
+DC ?= dmd
+LDC ?= ldc2
+GDC ?= gdc
+
+DMD_COMMON_FLAGS := -w $(IMPORTS)
 DMD_DEBUG_FLAGS := -debug -g $(DMD_COMMON_FLAGS)
 DMD_FLAGS := -O -inline $(DMD_COMMON_FLAGS)
 DMD_TEST_FLAGS := -unittest -g $(DMD_COMMON_FLAGS)
-LDC_FLAGS := -g -w -oq $(INCLUDE_PATHS)
-GDC_FLAGS := -g -w -oq $(INCLUDE_PATHS)
+LDC_FLAGS := -g -w -oq $(IMPORTS)
+GDC_FLAGS := -g -w -oq $(IMPORTS)
 override DMD_FLAGS += $(DFLAGS)
 override LDC_FLAGS += $(DFLAGS)
 override GDC_FLAGS += $(DFLAGS)
-DC ?= dmd
-LDC ?= ldc2
-GDC ?= gdc
 
-.PHONY: dmd ldc gdc test
+.PHONY: all clean install debug dmd ldc gdc githash pkg release test
 
-dmd: bin/dfmt
+all: bin/dfmt
 
 githash:
 	mkdir -p bin
 	git describe --tags > bin/githash.txt
 
+dmd: bin/dfmt
+
 ldc: githash
 	$(LDC) $(SRC) $(LDC_FLAGS) -ofbin/dfmt
 	-rm -f *.o
 
-gdc:githash
+gdc: githash
 	$(GDC) $(SRC) $(GDC_FLAGS) -obin/dfmt
 
 test: debug
@@ -46,8 +52,13 @@ pkg: dmd
 	$(MAKE) -f makd/Makd.mak pkg
 
 clean:
-	$(RM) bin/dfmt
+	$(RM) bin/dfmt bin/dfmt-test bin/githash.txt
+
+install:
+	chmod +x bin/dfmt
+	mkdir -p $(DESTDIR)$(PREFIX)/bin
+	cp -f bin/dfmt $(DESTDIR)$(PREFIX)/bin/dfmt
 
 release:
 	./release.sh
-	githash
+	$(MAKE) githash