Use xmalloc() and friends to catch allocation failures

Some places use the standard malloc/strdup without checking if the
allocation was successful; they should use xmalloc/xstrdup that
check the memory allocation result.

Signed-off-by: Dotan Barak <dotanba@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git.c

@@ -364,7 +364,7 @@ static void handle_internal_command(int argc, const char **argv)
 	if (sizeof(ext) > 1) {
 		i = strlen(argv[0]) - strlen(ext);
 		if (i > 0 && !strcmp(argv[0] + i, ext)) {
-			char *argv0 = strdup(argv[0]);
+			char *argv0 = xstrdup(argv[0]);
 			argv[0] = cmd = argv0;
 			argv0[i] = '\0';
 		}