print usage and exit with error on invalid arguments

Add also some testing to make sure help, long help and handling
of invalid arguments works as expected.

Based on pull request #19 originally by Laurent Arnoud (@spk).

src/apk.c

@@ -588,11 +588,11 @@ int main(int argc, char **argv)
 				help_requested = 1;
 				break;
 			}
-			if (r != -ENOTSUP) goto err_and_usage;
+			if (r != -ENOTSUP) goto err;
 		}
 	}
 
-	if (help_requested) {
+	if (help_requested || r == -ENOTSUP) {
 		r = usage(applet);
 		goto err;
 	}
@@ -686,12 +686,9 @@ int main(int argc, char **argv)
 	r = 0;
 #endif
 
-err_and_usage:
-	if (r == -EINVAL)
-		r = usage(applet);
+err:
 	if (r == -ESHUTDOWN)
 		r = 0;
-err:
 	if (ctx)
 		free(ctx);
 

test/command-parsing.sh

@@ -0,0 +1,26 @@
+#!/bin/sh
+
+fail=0
+
+help_output=$(../src/apk version --help 2>/dev/null)
+invalid_option_output="$(../src/apk --invalid-option version 2>/dev/null)"
+if [ "$help_output" != "$invalid_option_output" ]; then
+	echo "FAIL: invalid option does not trigger help"
+	fail=$((fail+1))
+fi
+
+if ! ../src/apk --help 2>/dev/null | grep -q "^Use apk --help --verbose for a full command listing."; then
+	echo "FAIL: brief help gives long help"
+	fail=$((fail+1))
+fi
+
+if ../src/apk --help --verbose 2>/dev/null | grep -q "^Use apk --help --verbose for a full command listing."; then
+	echo "FAIL: long help does not work"
+	fail=$((fail+1))
+fi
+
+if [ $fail -eq 0 ]; then
+	echo "OK: command parsing works"
+fi
+
+exit $fail