Makefile: set main.gitCommit when building

Makefile

@@ -9,12 +9,12 @@
 GOBIN = build/bin
 
 geth:
-	build/env.sh go install -v github.com/ethereum/go-ethereum/cmd/geth
+	build/env.sh go install -v $(shell build/ldflags.sh) ./cmd/geth
 	@echo "Done building."
 	@echo "Run \"$(GOBIN)/geth\" to launch geth."
 
 mist:
-	build/env.sh go install -v github.com/ethereum/go-ethereum/cmd/mist
+	build/env.sh go install -v $(shell build/ldflags.sh) ./cmd/mist
 	@echo "Done building."
 	@echo "Run \"$(GOBIN)/mist --asset_path=cmd/mist/assets\" to launch mist."
 

build/ldflags.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+set -e
+
+if [ ! -f "build/env.sh" ]; then
+    echo "$0 must be run from the root of the repository."
+    exit 2
+fi
+
+# set gitCommit when running from a Git checkout.
+if [ -f ".git/HEAD" ]; then
+    echo "-ldflags '-X main.gitCommit $(git rev-parse HEAD)'"
+fi