feat: add --color={always,never,auto} flag

src/cyan/cli.tl

@@ -54,6 +54,13 @@ parser:option("--gen-target", "Minimum targeted Lua version for generated code."
 parser:flag("--no-script", "Do not run any scripts.")
       :action(script.disable)
 
+parser:option("--color", "Colorize the output.", nil, nil, nil, nil)
+      :choices({ "never", "always", "auto" })
+      :default("auto")
+      :action(function(_: argparse.Args, __: string, val: string|boolean|{string})
+         log.set_color_mode(val as log.ColorMode)
+      end)
+
 parser:mutex(
    parser:flag("-q --quiet", "Do not print information messages to stdout. Errors may still be printed to stderr. (Same as --verbosity quiet).")
          :action(function()

src/cyan/log.tl

@@ -20,6 +20,7 @@
 --- create_logger: function(
 ---    stream: FILE,
 ---    verbosity_threshold: Verbosity,
+---    color_mode: ColorMode,
 ---    prefix: string | decoration.Decorated,
 ---    cont: string | decoration.Decorated,
 ---    inspector: function(any): string
@@ -65,7 +66,16 @@ local verbosity_to_int <total>: {Verbosity:integer} = {
    debug = 3,
 }
 
+---@desc
+--- Whether to apply color to the output
+local enum ColorMode
+   "always"
+   "never"
+   "auto"
+end
+
 local verbosity: Verbosity = "normal"
+local color_mode: ColorMode = "auto"
 local prefix_padding: integer = 10
 
 local inspect: function(any): string
@@ -101,6 +111,22 @@ local function is_a_tty(file: FILE): boolean
 end
 
 local function renderer(stream: FILE): decoration.Renderer
+   if color_mode == "always" then
+      if not is_a_tty(stream) then
+         return function(buf: {string}, content: string, decor: decoration.Decoration)
+            if decor then
+               decor.linked_uri = nil
+            end
+            decoration.render_ansi(buf, content, decor)
+         end
+      end
+
+      return decoration.render_ansi
+   end
+   if color_mode == "never" then
+      return decoration.render_plain
+   end
+
    if no_color_env or not is_a_tty(stream) then
       return decoration.render_plain
    end
@@ -348,6 +374,7 @@ local log <const> = {
    create_logger = create_logger,
    verbosities = verbosities,
    Verbosity = Verbosity,
+   ColorMode = ColorMode,
    Logger = Logger,
 }
 
@@ -357,6 +384,12 @@ function log.set_verbosity(level: Verbosity)
    verbosity = level
 end
 
+---@desc
+--- Globally set the color behavior of the logging module.
+function log.set_color_mode(mode: ColorMode)
+   color_mode = mode
+end
+
 ---@desc
 --- Globally set the padding of the prefixes of loggers.
 function log.set_prefix_padding(padding: integer)