Fix Tempo build-info (#295)

* Add missing build-info

Signed-off-by: Daniel González Lopes <danielgonzalezlopes@gmail.com>

* Use image-tag instead of version file

Signed-off-by: Daniel González Lopes <danielgonzalezlopes@gmail.com>

Makefile

@@ -1,3 +1,9 @@
+# Version number
+VERSION=$(shell ./tools/image-tag | cut -d, -f 1)
+
+GIT_REVISION := $(shell git rev-parse --short HEAD)
+GIT_BRANCH := $(shell git rev-parse --abbrev-ref HEAD)
+
 GOPATH := $(shell go env GOPATH)
 GORELEASER := $(GOPATH)/bin/goreleaser
 
@@ -14,7 +20,7 @@ ALL_DOC := $(shell find . \( -name "*.md" -o -name "*.yaml" \) \
 # ALL_PKGS is used with 'go cover'
 ALL_PKGS := $(shell go list $(sort $(dir $(ALL_SRC))))
 
-GO_OPT= -mod vendor
+GO_OPT= -mod vendor -ldflags "-X main.Branch=$(GIT_BRANCH) -X main.Revision=$(GIT_REVISION) -X main.Version=$(VERSION)"
 GOTEST_OPT?= -race -timeout 5m -count=1
 GOTEST_OPT_WITH_COVERAGE = $(GOTEST_OPT) -cover
 GOTEST=go test

cmd/tempo/main.go

@@ -25,7 +25,17 @@ import (
 
 const appName = "tempo"
 
+// Version is set via build flag -ldflags -X main.Version
+var (
+	Version  string
+	Branch   string
+	Revision string
+)
+
 func init() {
+	version.Version = Version
+	version.Branch = Branch
+	version.Revision = Revision
 	prometheus.MustRegister(version.NewCollector(appName))
 }