include git tag in binary when available

Makefile

@@ -1,16 +1,17 @@
 .PHONY: all install build release capdefs test smoke gofmt irctest
 
 GIT_COMMIT := $(shell git rev-parse HEAD 2> /dev/null)
+GIT_TAG := $(shell git tag --points-at HEAD 2> /dev/null | head -n 1)
 
 capdef_file = ./irc/caps/defs.go
 
 all: install
 
 install:
-	go install -v -ldflags "-X main.commit=$(GIT_COMMIT)"
+	go install -v -ldflags "-X main.commit=$(GIT_COMMIT) -X main.version=$(GIT_TAG)"
 
 build:
-	go build -v -ldflags "-X main.commit=$(GIT_COMMIT)"
+	go build -v -ldflags "-X main.commit=$(GIT_COMMIT) -X main.version=$(GIT_TAG)"
 
 release:
 	goreleaser --skip-publish --rm-dist