fast-{import,export}: use get_sha1_hex() to read from marks file

It's wrong to call get_sha1() if they should be SHA-1s, plus
inefficient.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Felipe Contreras

builtin/fast-export.c

@@ -623,7 +623,7 @@ static void import_marks(char *input_file)
 
 		mark = strtoumax(line + 1, &mark_end, 10);
 		if (!mark || mark_end == line + 1
-			|| *mark_end != ' ' || get_sha1(mark_end + 1, sha1))
+			|| *mark_end != ' ' || get_sha1_hex(mark_end + 1, sha1))
 			die("corrupt mark line: %s", line);
 
 		if (last_idnum < mark)

fast-import.c

@@ -1822,7 +1822,7 @@ static void read_marks(void)
 		*end = 0;
 		mark = strtoumax(line + 1, &end, 10);
 		if (!mark || end == line + 1
-			|| *end != ' ' || get_sha1(end + 1, sha1))
+			|| *end != ' ' || get_sha1_hex(end + 1, sha1))
 			die("corrupt mark line: %s", line);
 		e = find_object(sha1);
 		if (!e) {