Added Makefile

Makefile

@@ -0,0 +1,94 @@
+# The binaries to build (just the basenames).
+BINS := apg
+
+VERSION ?= $(shell grep VersionString apg.go | head -1 | awk '{print $$5}' | sed 's/"//g')
+ALL_PLATFORMS := darwin/amd64 linux/amd64 linux/arm linux/arm64 linux/ppc64le linux/s390x windows/amd64
+OS := $(if $(GOOS),$(GOOS),$(shell go env GOOS))
+ARCH := $(if $(GOARCH),$(GOARCH),$(shell go env GOARCH))
+TAG := $(VERSION)__$(OS)_$(ARCH)
+
+BIN_EXTENSION :=
+ifeq ($(OS), windows)
+  BIN_EXTENSION := .exe
+endif
+
+# If you want to build all binaries, see the 'all-build' rule.
+all: # @HELP builds binaries for one platform ($OS/$ARCH)
+all: build
+
+# For the following OS/ARCH expansions, we transform OS/ARCH into OS_ARCH
+# because make pattern rules don't match with embedded '/' characters.
+
+build-%:
+	@$(MAKE) build                        \
+	    --no-print-directory              \
+	    GOOS=$(firstword $(subst _, ,$*)) \
+	    GOARCH=$(lastword $(subst _, ,$*))
+
+all-build: # @HELP builds binaries for all platforms
+all-build: $(addprefix build-, $(subst /,_, $(ALL_PLATFORMS)))
+OUTBINS = $(foreach bin,$(BINS),bin/v$(VERSION)/$(OS)_$(ARCH)/$(bin)$(BIN_EXTENSION))
+build: $(OUTBINS)
+BUILD_DIRS := bin/v$(VERSION)/$(OS)_$(ARCH)     \
+              .go/bin/v$(VERSION)/$(OS)_$(ARCH) \
+              .go/cache
+
+# Each outbin target is just a facade for the respective stampfile target.
+# This `eval` establishes the dependencies for each.
+$(foreach outbin,$(OUTBINS),$(eval  \
+    $(outbin): .go/$(outbin).stamp  \
+))
+# This is the target definition for all outbins.
+$(OUTBINS):
+	@true
+
+# Each stampfile target can reference an $(OUTBIN) variable.
+$(foreach outbin,$(OUTBINS),$(eval $(strip   \
+    .go/$(outbin).stamp: OUTBIN = $(outbin)  \
+)))
+# This is the target definition for all stampfiles.
+# This will build the binary under ./.go and update the real binary iff needed.
+STAMPS = $(foreach outbin,$(OUTBINS),.go/$(outbin).stamp)
+.PHONY: $(STAMPS)
+$(STAMPS): go-build
+	@echo "binary: $(OUTBIN)"
+	@if ! cmp -s .go/$(OUTBIN) $(OUTBIN); then  \
+	    mv .go/$(OUTBIN) $(OUTBIN);             \
+	    date >$@;                               \
+	fi
+
+# This runs the actual `go build` which updates all binaries.
+go-build: $(BUILD_DIRS)
+	@echo
+	@echo "building for $(OS)/$(ARCH)"
+	@go build -o .go/bin/v$(VERSION)/$(OS)_$(ARCH)/apg$(BIN_EXTENSION) apg.go
+
+version: # @HELP outputs the version string
+version:
+	@echo $(VERSION)
+
+	    "
+
+$(BUILD_DIRS):
+	@mkdir -p $@
+
+clean: # @HELP removes built binaries and temporary files
+clean: bin-clean
+
+bin-clean:
+	rm -rf .go bin
+
+help: # @HELP prints this message
+help:
+	@echo "VARIABLES:"
+	@echo "  BINS = $(BINS)"
+	@echo "  OS = $(OS)"
+	@echo "  ARCH = $(ARCH)"
+	@echo "  REGISTRY = $(REGISTRY)"
+	@echo
+	@echo "TARGETS:"
+	@grep -E '^.*: *# *@HELP' $(MAKEFILE_LIST)    \
+	    | awk '                                   \
+	        BEGIN {FS = ": *# *@HELP"};           \
+	        { printf "  %-30s %s\n", $$1, $$2 };  \
+	    '