Update scripts per luacheck and add a script to run luacheck

.cfignore

@@ -0,0 +1 @@
+dev-utils

dev-utils/luacheck-scripts.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+
+# Spins up a docker container to run luacheck on the scripts directory.
+# Run this from the repo root (it uses pwd).
+
+# luacheck image tags include "latest" and "edge," "edge" being later than "latest"
+docker run -it --rm \
+      -v "$(pwd)/scripts:/code/scripts" \
+      pipelinecomponents/luacheck:latest luacheck scripts

scripts/README-luacheck.md

@@ -0,0 +1,8 @@
+# README: luacheck
+
+The `dev-utils/luacheck-scripts.sh` script will spin up a small docker container and run luacheck on all `.lua` files in this directory.
+
+luacheck documentation: https://luacheck.readthedocs.io/en/stable/config.html
+
+A `--luacheck:ignore` comment after a function declaration suppresses a warning about setting a global variable and that this is an unused function. (Scripts that are called only from fluent bit will appear to be unused.) It does _not_ tell luacheck to ignore the rest of the function. 
+

scripts/parse_keys_with_eq_pairs.lua

@@ -1,22 +1,25 @@
--- This parser is just a proof-of-concept. 
+-- These functions parse "tags" and "gauge" data into JSON key/value
+-- pairs. The "eq_pairs" of the function name are strings of
+-- non-whitespace (and non-=) characters separated by an equal sign.
 
-KEYS_TO_PARSE = {"tags", "gauge"}
+local KEYS_TO_PARSE = {"tags", "gauge"}
 
--- Splits a string of foo="bar" pairs and makes parsable json out of it. 
-function parse_keys_with_eq_pairs(tag, timestamp, record)
-    for k, v in pairs(KEYS_TO_PARSE) do
-        if (record[v] ~= nil) then 
+local eq_pairs_to_json_string = function (orig_string)
+    local new_string = string.gsub(orig_string, "(%S+)=(%S+)", "\"%1\":%2,")
+    -- trim off that last , and add curly braces around:
+    new_string = string.gsub(new_string, "(.+),$", "{%1}")
+    return new_string
+end
+
+-- Splits a string of foo="bar" pairs and makes parsable json out of it.
+function parse_keys_with_eq_pairs(tag, timestamp, record) --luacheck:ignore
+    for _, v in pairs(KEYS_TO_PARSE) do
+        if (record[v] ~= nil) then
             record[v] = eq_pairs_to_json_string(record[v])
 	end
     end
      -- 2 leaves timestamp unchanged
     return 2, timestamp, record
 end
 
-function eq_pairs_to_json_string(orig_string)
-    local new_string = string.gsub(orig_string, "(%S+)=(%S+)", "\"%1\":%2,")
-    -- trim off that last , and add curly braces around: 
-    new_string = string.gsub(new_string, "(.+),$", "{%1}")
-    return new_string
-end