test-dir-iterator: do not assume errno values

A few tests printed 'errno' as an integer and compared with
hardcoded integers; this is obviously not portable.

A two things to note are:

 - the string obtained by strerror() is not portable, and cannot be
   used for the purpose of these tests.

 - there unfortunately isn't a portable way to map error numbers to
   error names.

As we only care about a few selected errors, just map the error
number to the name before emitting for comparison.

Reported-by: Randall S. Becker <rsbecker@nexbridge.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/helper/test-dir-iterator.c

@@ -4,6 +4,15 @@
 #include "iterator.h"
 #include "dir-iterator.h"
 
+static const char *error_name(int error_number)
+{
+	switch (error_number) {
+	case ENOENT: return "ENOENT";
+	case ENOTDIR: return "ENOTDIR";
+	default: return "ESOMETHINGELSE";
+	}
+}
+
 /*
  * usage:
  * tool-test dir-iterator [--follow-symlinks] [--pedantic] directory_path
@@ -31,7 +40,7 @@ int cmd__dir_iterator(int argc, const char **argv)
 	diter = dir_iterator_begin(path.buf, flags);
 
 	if (!diter) {
-		printf("dir_iterator_begin failure: %d\n", errno);
+		printf("dir_iterator_begin failure: %s\n", error_name(errno));
 		exit(EXIT_FAILURE);
 	}
 

t/t0066-dir-iterator.sh

@@ -55,13 +55,13 @@ test_expect_success 'dir-iterator should list files in the correct order' '
 test_expect_success 'begin should fail upon inexistent paths' '
 	test_must_fail test-tool dir-iterator ./inexistent-path \
 		>actual-inexistent-path-output &&
-	echo "dir_iterator_begin failure: 2" >expected-inexistent-path-output &&
+	echo "dir_iterator_begin failure: ENOENT" >expected-inexistent-path-output &&
 	test_cmp expected-inexistent-path-output actual-inexistent-path-output
 '
 
 test_expect_success 'begin should fail upon non directory paths' '
 	test_must_fail test-tool dir-iterator ./dir/b >actual-non-dir-output &&
-	echo "dir_iterator_begin failure: 20" >expected-non-dir-output &&
+	echo "dir_iterator_begin failure: ENOTDIR" >expected-non-dir-output &&
 	test_cmp expected-non-dir-output actual-non-dir-output
 '