Teach --stdin option to "log" family

Move the logic to read revs from standard input that rev-list knows about
from it to revision machinery, so that all the users of setup_revisions()
can feed the list of revs from the standard input when "--stdin" is used
on the command line.

Allow some users of the revision machinery that want different semantics
from the "--stdin" option to disable it by setting an option in the
rev_info structure.

This also cleans up the kludge made to bundle.c via cut and paste.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-diff-tree.c

@@ -104,6 +104,7 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 	git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
 	opt->abbrev = 0;
 	opt->diff = 1;
+	opt->disable_stdin = 1;
 	argc = setup_revisions(argc, argv, opt, NULL);
 
 	while (--argc > 0) {