Add rustc/cargo version check

ci/version-check.sh

@@ -0,0 +1,35 @@
+#!/bin/bash -e
+
+require() {
+  declare expectedProgram="$1"
+  declare expectedVersion="$2"
+
+  read -r program version _ < <($expectedProgram -V)
+
+  declare ok=true
+  [[ $program = "$expectedProgram" ]] || ok=false
+  [[ $version =~ $expectedVersion ]] || ok=false
+
+  echo "Found $program $version"
+  if ! $ok; then
+    echo Error: expected "$expectedProgram $expectedVersion"
+    exit 1
+  fi
+}
+
+case ${1:-stable} in
+nightly)
+  require rustc 1.29.[0-9]+-nightly
+  require cargo 1.29.[0-9]+-nightly
+  ;;
+stable)
+  require rustc 1.28.[0-9]+
+  require cargo 1.28.[0-9]+
+  ;;
+*)
+  echo Error: unknown argument: "$1"
+  exit 1
+  ;;
+esac
+
+exit 0