Add version package and update the makefile

The makefile will grab the version info from git and pass it to the
linker so that version information based on tags, commits and commit
times is available in the code.

Makefile

@@ -3,6 +3,15 @@ BINARIES = $(patsubst cmd/%/,%,$(wildcard cmd/*/))
 
 .PHONY: all build test validate clean run $(BINARIES)
 
+VERSION := $(shell git describe --tags --always --dirty)
+COMMIT := $(shell git rev-parse --short HEAD)
+COMMIT_DATETIME := $(shell git log -1 --format=%cd --date=iso8601)
+
+LDFLAGS := -X git.omicron.one/omicron/linkshare/internal/version.Version=$(VERSION) \
+           -X git.omicron.one/omicron/linkshare/internal/version.GitCommit=$(COMMIT) \
+           -X "git.omicron.one/omicron/linkshare/internal/version.CommitDateTime=$(COMMIT_DATETIME)"
+
+
 all: build
 	
 
@@ -13,7 +22,7 @@ $(BINARY_DIR):
 	mkdir -p $(BINARY_DIR)
 
 $(BINARIES): %: $(BINARY_DIR)
-	go build -o $(BINARY_DIR)/$@ ./cmd/$@/
+	go build -ldflags '$(LDFLAGS)' -o $(BINARY_DIR)/$@ ./cmd/$@/
 
 test:
 	go test ./...