git-hooks: add pre-commit hook for fmt and testing checks.

git-hooks/pre-commit

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+set -e -x
+pushd () {
+    command pushd "$@" > /dev/null
+}
+
+popd () {
+    command popd "$@" > /dev/null
+}
+
+for workspace in rtchallenge rtiow; do
+  pushd ${workspace:?}
+  cargo fmt -- --check || (echo "To fix, run: cd ${workspace:?} && cargo fmt" && false)
+  popd
+done
+
+RT=rtchallenge
+AFFECTED="$(git diff-index --cached --name-only HEAD)"
+#echo "AFFECTED $AFFECTED"
+RT_AFFECTED=$(echo "${AFFECTED:?}" | grep ${RT:?} || true)
+if [ ! -z "$RT_AFFECTED" ]; then
+  echo "Files for the rt challenge were touched, running tests"
+  cd ${RT:?} && cargo build --examples && cargo test
+fi
+# Uncomment to debug presubmit.
+#exit 1