Use bool var to indicate negation instead of splitting operation again

Signed-off-by: rvandernoort <s.r.vandernoort@student.tudelft.nl>

libimage/filters.go

@@ -95,8 +95,11 @@ func (r *Runtime) compileImageFilters(ctx context.Context, options *ListImagesOp
 	for _, f := range options.Filters {
 		var key, value string
 		var filter filterFunc
+		negate := false
 		split := strings.SplitN(f, "!=", 2)
-		if len(split) != 2 {
+		if len(split) == 2 {
+			negate = true
+		} else {
 			split = strings.SplitN(f, "=", 2)
 			if len(split) != 2 {
 				return nil, errors.Errorf("invalid image filter %q: must be in the format %q", f, "filter=value or filter!=value")
@@ -185,7 +188,7 @@ func (r *Runtime) compileImageFilters(ctx context.Context, options *ListImagesOp
 		default:
 			return nil, errors.Errorf("unsupported image filter %q", key)
 		}
-		if len(strings.SplitN(f, "!=", 2)) == 2 {
+		if negate {
 			filter = negateFilter(filter)
 		}
 		filters[key] = append(filters[key], filter)