Fix funny types used in attribute value representation

It was bothering me a lot that I abused small integer values
casted to (void *) to represent non string values in
gitattributes.  This corrects it by making the type of attribute
values (const char *), and using the address of a few statically
allocated character buffer to denote true/false.  Unset attributes
are represented as having NULLs as their values.

Added in-header documentation to explain how git_checkattr()
routine should be called.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/diff.c b/diff.c
index a32078ea0..5f501864e 100644
--- a/diff.c
+++ b/diff.c
@@ -1069,7 +1069,7 @@ static int file_is_binary(struct diff_filespec *one)
 
 	setup_diff_attr_check(&attr_diff_check);
 	if (!git_checkattr(one->path, 1, &attr_diff_check)) {
-		void *value = attr_diff_check.value;
+		const char *value = attr_diff_check.value;
 		if (ATTR_TRUE(value))
 			return 0;
 		else if (ATTR_FALSE(value))
@@ -1078,7 +1078,7 @@ static int file_is_binary(struct diff_filespec *one)
 			;
 		else
 			die("unknown value %s given to 'diff' attribute",
-			    (char *)value);
+			    value);
 	}
 
 	if (!one->data) {