Fix arg parsing, move arg processing to cppo

Not quite finished with this, but the goal here is not have args being passed
in to the legacy cppo at all.  The g namespace is not ideal, but it does work
and it isolates the legacy code from needing to understand what's going on in
the shell level.  So we'll take advantage of that for the time being.

The bigger problem was that when I moved the arg parsing out of cppo, I failed
to move all of it--a block that checked the number of args got lost.  Restored.

blocksfree/legacy.py

@@ -87,6 +87,7 @@ g.DIRPATH = ""
 g.target_name = None
 g.target_dir = ""
 g.appledouble_dir = None
+g.image_file = None
 g.extract_file = None
 
 # runtime options
@@ -1030,7 +1031,7 @@ def hexdump(
 
 def run_cppo(args: list):
 	try:
-		disk = Disk(args[1])
+		disk = Disk(g.image_file)
 	except IOError as e:
 		log.critical(e)
 		quit_now(2)
@@ -1051,24 +1052,6 @@ def run_cppo(args: list):
 						"ShrinkIt archive.")
 				quit_now(2)
 
-	if len(args) == 4:
-		g.extract_file = args[2]
-
-	if g.extract_file:
-		targetPath = args[3]
-		if os.path.isdir(targetPath):
-			g.target_dir = targetPath
-		elif len(targetPath.rsplit("/", 1)) > 1:
-			g.target_dir, g.target_name = targetPath.rsplit("/", 1)
-		if not os.path.isdir(g.target_dir):
-			print("Target directory {} not found.".format(g.target_dir))
-			quit_now(2)
-	else:
-		if not g.catalog_only:
-			if not os.path.isdir(args[2]):
-				print("Target directory not found.")
-				quit_now(2)
-
 	if g.src_shk:
 		g.prodos_names = False
 		if not g.catalog_only:
@@ -1222,7 +1205,8 @@ def run_cppo(args: list):
 	if (not g.src_shk and not g.dos33 and g.extract_file
 			and (args[2][0] not in ('/', ':'))):
 		log.critical("Cannot extract {} from {}: "
-				"ProDOS volume name required".format(args[2], args[1]))
+				"ProDOS volume name required".format(
+					g.extract_file, g.image_file))
 		quit_now(2)
 
 	if g.dos33:

cppo

@@ -45,6 +45,7 @@ Wildcard matching (*) is not supported and images are not validated.
 ShrinkIt support requires Nulib2. cppo requires Python 2.6+ or 3.0+."""
 
 import sys
+import os
 
 from blocksfree.legacy import g
 import blocksfree.legacy
@@ -98,6 +99,35 @@ def cppo(args: list):
 		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()
+
+	g.image_file = args[1]
+
+	if len(args) == 4:
+		g.extract_file = args[2]
+
+	if g.extract_file:
+		target_path = args[3]
+		if os.path.isdir(target_path):
+			g.target_dir = target_path
+		elif len(target_path.rsplit("/", 1)) > 1:
+			g.target_dir, g.target_name = target_path.rsplit("/", 1)
+		if not os.path.isdir(g.target_dir):
+			log.critical("Directory {} not found.".format(g.target_dir))
+			sys.exit(2)
+	else:
+		if not g.catalog_only:
+			if not os.path.isdir(args[2]):
+				log.critical("Directory {} not found.".format(g.target_dir))
+				sys.exit(2)
+
 	blocksfree.legacy.run_cppo(args)
 
 if __name__ == '__main__':