test: use shellcheck to check most shell code

Split the Bash template into smaller files that don't use templating,
and check those file. Fix the couple of things shellcheck complained
about.

1 files changed, 2 insertions, 0 deletions

diff --git a/echo.sh b/echo.sh
index 44f272a..0564d42 100644
--- a/echo.sh
+++ b/echo.sh
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 _run()
 {
     if "$@" < /dev/null > stdout 2> stderr