test 'DESTDIR=/dir/here make install' support (#438)

tests/test_make_install.bats

@@ -0,0 +1,14 @@
+#!/usr/bin/env bats
+
+
+INSTALL_BASE="/tmp/git-secret-test-install"
+
+@test "install git-secret to '$INSTALL_BASE'" {
+
+  rm -f "${INSTALL_BASE}/usr/bin/git-secret"
+
+  cd $SECRET_PROJECT_ROOT && DESTDIR="${INSTALL_BASE}" make install
+
+  [ -x "${INSTALL_BASE}/usr/bin/git-secret" ]
+}
+