Check return value of ftruncate call in http.c

In new_http_object_request(), check ftruncate() call return value and
handle possible errors.

Signed-off-by: Jeff Lasslett <jeff.lasslett@gmail.com>
Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http.c

@@ -1187,7 +1187,11 @@ struct http_object_request *new_http_object_request(const char *base_url,
 		if (prev_posn>0) {
 			prev_posn = 0;
 			lseek(freq->localfile, 0, SEEK_SET);
-			ftruncate(freq->localfile, 0);
+			if (ftruncate(freq->localfile, 0) < 0) {
+				error("Couldn't truncate temporary file %s for %s: %s",
+					  freq->tmpfile, freq->filename, strerror(errno));
+				goto abort;
+			}
 		}
 	}