mu: add --uncooked option for mu extract

To avoid replacing spaces with dashes

Fixes #2434.

man/mu-extract.1.org

@@ -51,6 +51,11 @@ directory.
 overwrite existing files with the same name; by default overwriting is not
 allowed.
 
+** -u,--uncooked
+by default, ~mu~ transforms the attachment filenames a bit (such as by replacing
+spaces by dashes); with this option, leave that to the minimum for creating
+a legal filename in the target directory.
+
 ** --play
 Try to 'play' (open) the attachment with the default application for the
 particular file type. On MacOS, this uses the *open* program, on other platforms

mu/mu-cmd-extract.cc

@@ -33,8 +33,12 @@ save_part(const Message::Part& part, size_t idx, const Options& opts)
 		const auto tdir{opts.extract.targetdir};
 		return tdir.empty() ? tdir : tdir + G_DIR_SEPARATOR_S;
 	});
+
+	/* 'uncooked' isn't really _raw_; it means only doing some _minimal_
+	 * cooking */
 	const auto path{targetdir +
-		part.cooked_filename().value_or(format("part-%zu", idx))};
+		part.cooked_filename(opts.extract.uncooked)
+		.value_or(format("part-%zu", idx))};
 
 	if (auto&& res{part.to_file(path, opts.extract.overwrite)}; !res)
 		return Err(res.error());

mu/mu-options.cc

@@ -222,6 +222,8 @@ sub_extract(CLI::App& sub, Options& opts)
 	sub.add_option("message", opts.extract.message,
 		       "Path to message file")->required()
 		->type_name("<message-path>");
+	sub.add_flag("--uncooked,-u", opts.extract.uncooked,
+		       "Avoid massaging extracted file-names");
 	sub.add_option("filename-rx", opts.extract.filename_rx,
 		       "Regular expression for files to save")
 		->type_name("<filename-rx>")

mu/mu-options.hh

@@ -126,6 +126,8 @@ struct Options {
 		bool		overwrite;		/**<  overwrite same-named files */
 		bool		play;			/**<  try to 'play' attachment */
 		std::string     filename_rx;		/**<  Filename rx to save */
+		bool            uncooked{};             /**<  Whether to avoid massaging
+							 * output filename */
 	} extract;
 
 	/*