Re: [PATCH v7 3/6] fast-import: add feature command

["Shawn O. Pearce" <spearce@spearce.org>]

Sverre Rabbelier <srabbelier@gmail.com> wrote:
> This allows the fronted to require a specific feature to be supported
> by the frontend, or abort.
>
> Also add support for the first feature, date-format=.
...
> +`feature`
> +~~~~~~~~~
> +Require that fast-import supports the specified feature, or abort if
> +it does not.
> +
> +....
> +	'feature' SP <feature> LF
> +....
> +
> +The <feature> part of the command may be any string matching
> +[a-zA-Z-] and should be understood by a version of fast-import.
> +

Where is the documentation for 'feature date-format=<FORMAT>'?

Also, IIRC the fast-import list agreed that the <feature> name must
match the re ^[a-zA-Z][a-zA-Z-]*$.  Saying that here does somewhat
help another fast-import developer to use the same stream format,
but it does not help a user to understand what features they can
ask for in their stream.

> diff --git a/fast-import.c b/fast-import.c
> index 812fcf0..9bf06a4 100644
> --- a/fast-import.c
> +++ b/fast-import.c
> @@ -2450,6 +2450,17 @@ static void parse_one_option(const char *option)
>  	}
>  }
>  
> +static void parse_feature(void)
> +{
> +	char *feature = command_buf.buf + 8;
> +
> +	if (!prefixcmp(feature, "date-format=")) {
> +		option_date_format(feature + 12);
> +	} else {
> +		die("This version of fast-import does not support feature %s.", feature);
> +	}
> +}
> +
>  static int git_pack_config(const char *k, const char *v, void *cb)
>  {
>  	if (!strcmp(k, "pack.depth")) {
> @@ -2526,6 +2537,8 @@ int main(int argc, const char **argv)
>  			parse_checkpoint();
>  		else if (!prefixcmp(command_buf.buf, "progress "))
>  			parse_progress();
> +		else if (!prefixcmp(command_buf.buf, "feature "))
> +			parse_feature();

So its legal to change the data format in the middle of a stream?
I thought we agreed on fast-import list that "feature" needs to come
before any data commands, and isn't legal once data commands have
appeared in the stream.  Thus it should not be possible to request
a change in the date-format once a blob or commit has been stored.

-- 
Shawn.