read_revisions_from_stdin: make copies for handle_revision_arg

read_revisions_from_stdin() has passed pointers to its read buffer
down to handle_revision_arg() since its inception way back in 42cabc34
(Teach rev-list an option to read revs from the standard input.,
2006-09-05).  Even back then, this was a bug: through
add_pending_object, the argument was recorded in the object_array's
'name' field.

Fix it by making a copy whenever read_revisions_from_stdin() passes an
argument down the callchain.  The other caller runs handle_revision_arg()
on argv[], where it would be redundant to make a copy.
Signed-off-by: NThomas Rast <trast@inf.ethz.ch>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

revision.c

@@ -1275,7 +1275,8 @@ static void read_revisions_from_stdin(struct rev_info *revs,
 			}
 			die("options not supported in --stdin mode");
 		}
-		if (handle_revision_arg(sb.buf, revs, 0, REVARG_CANNOT_BE_FILENAME))
+		if (handle_revision_arg(xstrdup(sb.buf), revs, 0,
+					REVARG_CANNOT_BE_FILENAME))
 			die("bad revision '%s'", sb.buf);
 	}
 	if (seen_dashdash)