Add luacheck + fix warnings detected by it

.luacheckrc

@@ -0,0 +1,4 @@
+std = "lua51+luajit+minetest"
+
+globals = {"test_string_to_table"}
+read_globals = {"DIR_DELIM"}

alg1.lua

@@ -1,9 +1,8 @@
 local function stringToTable(str)
     local parseTable -- defined later, but we need it in parseValue
 
-    local function parseValue(s, i)
-        s = s:match("^%s*(.-)%s*$", i) -- Trim leading/trailing spaces
-        i = 1
+    local function parseValue(s, idx)
+        s = s:match("^%s*(.-)%s*$", idx) -- Trim leading/trailing spaces
 
         if s:sub(1, 1) == "{" then
             return parseTable(s)
@@ -47,7 +46,6 @@ local function stringToTable(str)
 
     local function parseKey(s, i)
         s = s:match("^%s*(.-)%s*$", i) -- Trim leading/trailing spaces
-        i = 1
         if s:find("^[%a_]") then
             local key = s:match("^[%a%d_]*")
             if key ~= "true" and key ~= "false" and key ~= "nil" then

alg2.lua

@@ -55,7 +55,6 @@ local function codedStringToTable(str)
     local tbl = {}
     local key, value
     local next_key = 1
-    local inKey = true
     local depth = 0
     local buffer = ""
 
@@ -70,7 +69,7 @@ local function codedStringToTable(str)
 
     for i = 1, #str do
         local char = str:sub(i, i)
-        
+
         if char == '{' then
             if depth > 0 then
                 buffer = buffer .. char

algtour.lua

@@ -45,7 +45,7 @@ local function parse_key(str)
         if not success then
             return false, key
         end
-        if key == nil then 
+        if key == nil then
             return false, "nil cannot be a key"
         end
         return true, key
@@ -95,7 +95,7 @@ local function stringToTable(str)
     local success = true
     local tbl
 
-    local replacements = 0
+    local replacements
     local table_count = 0
     repeat
         str, replacements = str:gsub("({[^{}]*})", function (match)

init.lua

@@ -18,7 +18,7 @@ local tests = {
     "{key1 = 123, key2 = true, key3 = {nestedKey1 = 'value1', nestedKey2 = false}}",
     "{}", "{ }",
     "{[{'tables can be'}] = 'keys too'}",
-    '{\'{table = "that", "contains", a = "string", ["looking"] = {"like", "a"; "table"}}\'}',   
+    '{\'{table = "that", "contains", a = "string", ["looking"] = {"like", "a"; "table"}}\'}',
     '{[-42.42e42] = 42.42E-42}',
     '{1, 2, 3, }',
     -- invalid tables, the code should return an error