feat: Add version print

Makefile

@@ -4,6 +4,28 @@ COMMON_SELF_DIR := $(dir $(lastword $(MAKEFILE_LIST)))
 ROOT_DIR := $(abspath $(shell cd $(COMMON_SELF_DIR)/ && pwd -P))
 OUTPUT_DIR := $(ROOT_DIR)/_output
 
+# ==============================================================================
+# Version
+
+VERSION_PACKAGE=git.vinchent.xyz/vinchent/howmuch/pkg/version
+
+ifeq ($(origin VERSION), undefined)
+	VERSION:=$(shell git describe --tags --always --match='v*')
+endif
+
+GIT_TREE_STATE="dirty"
+ifeq (, $(shell git status --porcelain 2>/dev/null))
+	GIT_TREE_STATE ="clean"
+endif
+
+GIT_COMMIT:=$(shell git rev-parse HEAD)
+
+GO_LDFLAGS += \
+	-X $(VERSION_PACKAGE).GitVersion=$(VERSION) \
+	-X $(VERSION_PACKAGE).GitCommit=$(GIT_COMMIT) \
+	-X $(VERSION_PACKAGE).GitTreeState=$(GIT_TREE_STATE) \
+	-X $(VERSION_PACKAGE).BuildDate=$(shell date -u +'%Y-%m-%dT%H:%M:%SZ')
+
 # ==============================================================================
 .PHONY: all
 all: add-copyright format build
@@ -12,7 +34,7 @@ all: add-copyright format build
 
 .PHONY: build
 build: tidy # build.
-	@go build -v -o $(OUTPUT_DIR)/howmuch $(ROOT_DIR)/cmd/howmuch/main.go
+	@go build -v -ldflags "$(GO_LDFLAGS)" -o $(OUTPUT_DIR)/howmuch $(ROOT_DIR)/cmd/howmuch/main.go
 
 .PHONY: format
 format: # format code.