Add initial version of xz --list.

This is a bit rough but should be useful for basic things.
Ideas (with detailed examples) about the output format are
welcome.

The output of --robot --list is not necessarily stable yet,
although I don't currently have any plans about changing it.

The man page hasn't been updated yet.

src/xz/Makefile.am

@@ -16,6 +16,7 @@ xz_SOURCES = \
 	file_io.h \
 	hardware.c \
 	hardware.h \
+	list.c \
 	main.c \
 	main.h \
 	message.c \

src/xz/list.h

@@ -0,0 +1,18 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       list.h
+/// \brief      List information about .xz files
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+/// \brief      List information about the given .xz file
+extern void list_file(const char *filename);
+
+
+/// \brief      Show the totals after all files have been listed
+extern void list_totals(void);

src/xz/main.c

@@ -153,10 +153,7 @@ main(int argc, char **argv)
 	args_info args;
 	args_parse(&args, argc, argv);
 
-	if (opt_mode == MODE_LIST)
-		message_fatal("--list is not implemented yet.");
-
-	if (opt_robot)
+	if (opt_mode != MODE_LIST && opt_robot)
 		message_fatal(_("Compression and decompression with --robot "
 			"are not supported yet."));
 
@@ -184,6 +181,11 @@ main(int argc, char **argv)
 	// line arguments.
 	signals_init();
 
+	// coder_run() handles compression, decopmression, and testing.
+	// list_file() is for --list.
+	void (*run)(const char *filename) = opt_mode == MODE_LIST
+			 ? &list_file : &coder_run;
+
 	// Process the files given on the command line. Note that if no names
 	// were given, parse_args() gave us a fake "-" filename.
 	for (size_t i = 0; i < args.arg_count && !user_abort; ++i) {
@@ -218,7 +220,7 @@ main(int argc, char **argv)
 		}
 
 		// Do the actual compression or uncompression.
-		coder_run(args.arg_names[i]);
+		run(args.arg_names[i]);
 	}
 
 	// If --files or --files0 was used, process the filenames from the
@@ -234,13 +236,18 @@ main(int argc, char **argv)
 
 			// read_name() doesn't return empty names.
 			assert(name[0] != '\0');
-			coder_run(name);
+			run(name);
 		}
 
 		if (args.files_name != stdin_filename)
 			(void)fclose(args.files_file);
 	}
 
+	// All files have now been handled. If in --list mode, display
+	// the totals before exiting.
+	if (opt_mode == MODE_LIST)
+		list_totals();
+
 	// If we have got a signal, raise it to kill the program instead
 	// of calling tuklib_exit().
 	signals_exit();

src/xz/private.h

@@ -48,3 +48,4 @@
 #include "signals.h"
 #include "suffix.h"
 #include "util.h"
+#include "list.h"