Re: [PATCH v2 3/9] protocol: introduce protocol extention mechanisms

> Brandon Williams <bmwill@google.com> writes:
> 
> > +`GIT_PROTOCOL`::
> > +	For internal use only.  Used in handshaking the wire protocol.
> > +	Contains a colon ':' separated list of keys with optional values
> > +	'key[=value]'.  Presence of unknown keys must be tolerated.
> 
> Is this meant to be used only on the "server" end?  Am I correct to
> interpret "handshaking" to mean the initial connection acceptor
> (e.g. "git daemon") uses it to pass what it decided to the programs
> that implement the service (e.g. "git receive-pack")?

> 
> > +/*
> > + * Environment variable used in handshaking the wire protocol.
> > + * Contains a colon ':' separated list of keys with optional values
> > + * 'key[=value]'.  Presence of unknown keys must be tolerated.
> > + */
> > +#define GIT_PROTOCOL_ENVIRONMENT "GIT_PROTOCOL"
> 
> "Must be tolerated" feels a bit strange.  When somebody asks you to
> use "version 3" or "version 1 variant 2", when you only know
> "version 0" or "version 1" and you are not yet even aware of the
> concept of "variant", we simply ignore "variant=2" as if it wasn't
> there, even though "version=3" will be rejected (because we know of
> "version"; it's just that we don't know "version=3").

> 
> > +enum protocol_version determine_protocol_version_server(void)
> > +{
> > +	const char *git_protocol = getenv(GIT_PROTOCOL_ENVIRONMENT);
> > +	enum protocol_version version = protocol_v0;
> > +
> > +	if (git_protocol) {
> > +		struct string_list list = STRING_LIST_INIT_DUP;
> > +		const struct string_list_item *item;
> > +		string_list_split(&list, git_protocol, ':', -1);
> > +
> > +		for_each_string_list_item(item, &list) {
> > +			const char *value;
> > +			enum protocol_version v;
> > +
> > +			if (skip_prefix(item->string, "version=", &value)) {
> > +				v = parse_protocol_version(value);
> > +				if (v > version)
> > +					version = v;
> > +			}
> > +		}
> > +
> > +		string_list_clear(&list, 0);
> > +	}
> > +
> > +	return version;
> > +}
> 
> This implements "the largest one wins", not "the last one wins".  Is
> there a particular reason why the former is chosen?
>