Subject: Re: [PATCH v2 2/4] update-index: use the same structure for chmod as add

From: Junio C Hamano <[email-masked]>
Date: Sun, 11 Sep 2016 15:28:27 -0700

Thomas Gummerer <[email-masked]> writes:

> @@ -955,10 +941,8 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
>  			PARSE_OPT_NOARG | /* disallow --cacheinfo=<mode> form */
>  			PARSE_OPT_NONEG | PARSE_OPT_LITERAL_ARGHELP,
>  			(parse_opt_cb *) cacheinfo_callback},
> -		{OPTION_CALLBACK, 0, "chmod", &set_executable_bit, N_("(+/-)x"),
> -			N_("override the executable bit of the listed files"),
> -			PARSE_OPT_NONEG | PARSE_OPT_LITERAL_ARGHELP,
> -			chmod_callback},
> +		OPT_STRING( 0, "chmod", &chmod_arg, N_("(+/-)x"),
> +			N_("override the executable bit of the listed files")),
>  		{OPTION_SET_INT, 0, "assume-unchanged", &mark_valid_only, NULL,
>  			N_("mark files as \"not changing\""),
>  			PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, MARK_FLAG},
> @@ -1018,6 +1002,15 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
>  	if (argc == 2 && !strcmp(argv[1], "-h"))
>  		usage_with_options(update_index_usage, options);
>  
> +	if (!chmod_arg)
> +		force_mode = 0;
> +	else if (!strcmp(chmod_arg, "-x"))
> +		force_mode = 0666;
> +	else if (!strcmp(chmod_arg, "+x"))
> +		force_mode = 0777;
> +	else
> +		die(_("option 'chmod' expects \"+x\" or \"-x\""));
> +

I am afraid that this changes the behaviour drastically.

"git update-index" is an oddball command that takes options and then
processes them immediately, exactly because it was designed to take

	git update-index --chmod=-x A --chmod=+x B --add C

and say things like "A and B are not in the index and you are
attempting to add them before giving me --add option".

	git update-index --add --chmod=-x A --chmod=+x B C

is expected to add A as non-executable, and B and C as executable.
Many exotic parse-options callback mechanisms used in this command
were invented exactly to support its quirky way of not doing "get a
list of options and use the last one".  And this patch breaks it for
only one option without changing the others.

If we were willing to take such a big backward compatiblity hit in
the upcoming release (which I personally won't be affected, but old
scripts by others need to be audited and adjusted, which I won't
volunteer to do myself), we should make such a change consistently,
e.g. "git update-index A --add --remove B" should no longer error
out when it sees A and it is not yet in the index because "--add"
hasn't been given yet, or A is in the index but is missing from the
working tree because "--remove" hasn't been given yet.  Then it may
be more justifiable if "update-index --chmod=-x A --chmod=+x B"
added A as an executable.  With the current form of this patch, it
is not.

Can we do this "fix" without this change?