patch current and add new shellcheck recipe

new shellcheck recipe is focused on shellcheck'ing the recipes within
the justfile itself. As they get more complicated, it is helpful to make
sure that we maintain good shell style.

Don't leave shellchecks early on an error so that we can make sure that
the temporary files that are spawned are removed.

justfile

@@ -172,10 +172,19 @@ format-just:
 # check the scripts for common errors and bugs
 shellcheck:
     #!/usr/bin/env sh
-    set -exu
+    set -x
     format_list=$(mktemp)
     git ls-tree -r HEAD | awk '{ if ($1 == 100755 || $4 ~ /\.sh/) print $4 }' > ${format_list}
     shellcheck --severity style --shell sh $(cat ${format_list})
+    rm "${format_list}"
+
+# check a script recipe also using shellcheck
+shellcheck-recipe RECIPE:
+    #!/usr/bin/env sh
+    source=$(mktemp)
+    just -n {{ RECIPE }} 2> "${source}"
+    shellcheck --severity style --shell sh "${source}"
+    rm "${source}"
 
 # below are the mimics of ldmx <cmd>
 # we could think about removing them if folks are happy with committing to the