Move argument parsing out of legacy.py

The point is to separate the CLI interface to cppo from the inner logic so that
we can begin replacing the legacy code with proper implementations thereof.
This isn't 100% complete in that regard--we still need to pass args to the
legacy main function--but the part of cppo that will survive this whole process
is now functionally isolated from the part that's likely to get replaced to a
large degree.

blocksfree/legacy.py

@@ -776,10 +776,6 @@ def quit_now(exitcode=0):
 				shutil.rmtree('/tmp' + "/" + file)
 	sys.exit(exitcode)
 
-def usage(exitcode=1):
-	print(sys.modules[__name__].__doc__)
-	quit_now(exitcode)
-
 def to_sys_name(name):
 	if os.name == 'nt':
 		if name[-1] == '.':
@@ -1033,59 +1029,6 @@ def hexdump(
 
 
 def run_cppo(args: list):
-	while True: # breaks when there are no more arguments starting with dash
-		if len(args) == 1:
-			usage()
-
-		elif args[1][0] != '-':
-			break
-
-		elif args[1] == '-s':
-			g.afpsync_msg = False
-			args = args[1:]
-
-		elif args[1] == '-n':
-			g.extract_in_place = True
-			args = args[1:]
-
-		elif args[1] == '-uc':
-			g.casefold_upper = True
-			args = args[1:]
-
-		elif args[1] == '-ad':
-			g.use_appledouble = True
-			g.prodos_names = True
-			args = args[1:]
-
-		elif args[1] == '-shk':
-			g.src_shk = True
-			args = args[1:]
-
-		elif args[1] == '-pro':
-			g.prodos_names = True
-			args = args[1:]
-
-		elif args[1] == '-e':
-			g.use_extended = True
-			g.prodos_names = True
-			args = args[1:]
-
-		elif args[1] == '-cat':
-			g.catalog_only = True
-			args = args[1:]
-
-		else:
-			usage()
-
-	if g.use_appledouble and g.use_extended:
-		usage()
-	if g.catalog_only:
-		if len(args) != 2:
-			usage()
-	else:
-		if len(args) not in (3, 4):
-			usage()
-
 	try:
 		disk = Disk(args[1])
 	except IOError as e:
@@ -1279,7 +1222,9 @@ def run_cppo(args: list):
 	# enforce leading slash if ProDOS
 	if (not g.src_shk and not g.dos33 and g.extract_file
 			and (args[2][0] not in ('/', ':'))):
-		usage()
+		log.critical("Cannot extract {} from {}: "
+				"ProDOS volume name required".format(args[2], args[1]))
+		quit_now(2)
 
 	if g.dos33:
 		disk_name = (disk.diskname

cppo

@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+# vim: set tabstop=4 shiftwidth=4 noexpandtab filetype=python:
+
+# Copyright (C) 2013-2016  Ivan Drucker
+# Copyright (C) 2017       T. Joseph Carter
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation; either version 2 of the License, or (at your
+# option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+# for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+#
+#
+# If interested, please see the file HISTORY.md for information about both the
+# technical and licensing decisions that have gone into the rewriting of cppo.
+
+"""cppo: Copy/catalog files from a ProDOS/DOS 3.3/ShrinkIt image/archive.
+
+copy all files: cppo [options] imagefile target_directory
+copy one file : cppo [options] imagefile /extract/path target_path
+catalog image : cppo -cat [options] imagefile
+
+options:
+-shk: ShrinkIt archive as source (also auto-enabled by filename).
+-ad : Netatalk-compatible AppleDouble metadata files and resource forks.
+-e  : Nulib2-compatible filenames with type/auxtype and resource forks.
+-uc : Copy GS/OS mixed case filenames as uppercase.
+-pro: Adapt DOS 3.3 names to ProDOS and remove addr/len from file data.
+
+/extract/path examples:
+    /FULL/PRODOS/PATH (ProDOS image source)
+    "MY FILENAME" (DOS 3.3 image source)
+    Dir:SubDir:FileName (ShrinkIt archive source)
+
++ after a file name indicates a GS/OS or Mac OS extended (forked) file.
+Wildcard matching (*) is not supported and images are not validated.
+ShrinkIt support requires Nulib2. cppo requires Python 2.6+ or 3.0+."""
+
+import sys
+
+from blocksfree.legacy import g
+import blocksfree.legacy
+
+def usage(exitcode=1):
+	print(sys.modules[__name__].__doc__)
+	sys.exit(exitcode)
+
+def cppo(args: list):
+	while True: # breaks when there are no more arguments starting with dash
+		if len(args) == 1:
+			usage()
+
+		elif args[1][0] != '-':
+			break
+
+		elif args[1] == '-s':
+			g.afpsync_msg = False
+			args = args[1:]
+
+		elif args[1] == '-n':
+			g.extract_in_place = True
+			args = args[1:]
+
+		elif args[1] == '-uc':
+			g.casefold_upper = True
+			args = args[1:]
+
+		elif args[1] == '-ad':
+			g.use_appledouble = True
+			g.prodos_names = True
+			args = args[1:]
+
+		elif args[1] == '-shk':
+			g.src_shk = True
+			args = args[1:]
+
+		elif args[1] == '-pro':
+			g.prodos_names = True
+			args = args[1:]
+
+		elif args[1] == '-e':
+			g.use_extended = True
+			g.prodos_names = True
+			args = args[1:]
+
+		elif args[1] == '-cat':
+			g.catalog_only = True
+			args = args[1:]
+
+		else:
+			usage()
+
+	blocksfree.legacy.run_cppo(args)
+
+if __name__ == '__main__':
+	cppo(sys.argv)