Introduce semantic versioning.

This introduces semantic versioning (http://semver.org/) in Prometheus:

- A new VERSION file contains the semantic version string.

- The "tarball" target now includes versioning and build information in
  the tarball name, like: "prometheus-0.1.0.linux-amd64.tar.gz".

- A new "release" target allows scp-ing the versioned tarball to a
  remote machine (file server).

- A new "tag" target allows git-tagging the current revision with the
  version specified in VERSION.

Change-Id: I1f19f38b9b317bfa9eb513754750df5a9c602d94

Makefile

@@ -34,8 +34,19 @@ build: config dependencies model preparation tools web
 docker: build
 	docker build -t prometheus:$(REV) .
 
-tarball: build
+tarball: $(ARCHIVE)
-	tar -C $(BUILD_PATH)/package -czf prometheus.tar.gz .
+
+$(ARCHIVE): build
+	tar -C $(BUILD_PATH)/package -czf $(ARCHIVE) .
+
+release: REMOTE     ?= $(error "can't upload, REMOTE not set")
+release: REMOTE_DIR ?= $(error "can't upload, REMOTE_DIR not set")
+release: $(ARCHIVE)
+	scp $< $(REMOTE):$(REMOTE_DIR)/
+
+tag:
+	git tag $(VERSION)
+	git push --tags
 
 $(BUILD_PATH)/cache/$(GOPKG):
 	curl -o $@ $(GOURL)/$(GOPKG)
@@ -101,4 +112,4 @@ update:
 web: config dependencies model preparation
 	$(MAKE) -C web
 
-.PHONY: advice binary build clean config dependencies documentation format model package preparation race_condition_binary race_condition_run run search_index tarball test tools update
+.PHONY: advice binary build clean config dependencies documentation format model preparation race_condition_binary race_condition_run release run search_index tag tarball test tools update

Makefile.INCLUDE

@@ -78,12 +78,14 @@ BREW_INSTALL := brew install
 # Set WGET_OPTIONS to include ``--no-use-server-timestamps`` to alleviate this.
 WGET := wget $(WGET_OPTIONS) -c
 
+VERSION    := $(shell cat VERSION)
 REV        := $(shell git rev-parse --short HEAD)
 BRANCH     := $(shell git rev-parse --abbrev-ref HEAD)
 HOSTNAME   := $(shell hostname -f)
 BUILD_DATE := $(shell date +%Y%m%d-%H:%M:%S)
 BUILDFLAGS := -ldflags \
-	      " -X main.buildVersion $(REV)\
+	      " -X main.buildVersion $(VERSION)\
+		-X main.buildRevision $(REV)\
 		-X main.buildBranch $(BRANCH)\
 		-X main.buildUser $(USER)@$(HOSTNAME)\
 		-X main.buildDate $(BUILD_DATE)\
@@ -93,3 +95,5 @@ BUILDFLAGS := -ldflags \
 		-X main.snappyVersion $(SNAPPY_VERSION)"
 
 PROTOC := $(LOCAL_BINARIES)/protoc
+
+ARCHIVE := prometheus-$(VERSION).$(GOOS)-$(GOARCH).tar.gz

VERSION

@@ -0,0 +1 @@
+0.1.0

build_info.go

@@ -20,6 +20,7 @@ import (
 // Build information. Populated by Makefile.
 var (
 	buildVersion    string
+	buildRevision   string
 	buildBranch     string
 	buildUser       string
 	buildDate       string
@@ -33,6 +34,7 @@ var (
 // via go tool ld such that this can be reported on-demand.
 var BuildInfo = map[string]string{
 	"version":          buildVersion,
+	"revision":         buildRevision,
 	"branch":           buildBranch,
 	"user":             buildUser,
 	"date":             buildDate,
@@ -43,7 +45,7 @@ var BuildInfo = map[string]string{
 }
 
 var versionInfoTmpl = template.Must(template.New("version").Parse(
-	`prometheus, version {{.version}} ({{.branch}})
+	`prometheus, version {{.version}} (branch: {{.branch}}, revision: {{.revision}})
   build user:       {{.user}}
   build date:       {{.date}}
   go version:       {{.go_version}}