Re: Request for detailed documentation of git pack protocol

From: Jakub Narebski <jnareb@gmail.com>
Date: Jun 4, 2009, 08:45 UTC
Message-ID: <200906041045.11328.jnareb@gmail.com>
In-Reply-To: <alpine.LSU.2.00.0906032240300.31588@hermes-2.csi.cam.ac.uk>

Dnia środa 3. czerwca 2009 23:53, Tony Finch napisał:

Show 13 quoted lines

> On Wed, 3 Jun 2009, Jakub Narebski wrote:
> >
> > Actually git accepts both lowercase and uppercase in HEXDIG (at least
> > for pkt-length), but it prefers lowercase.
> 
> You should ensure that all hex digit strings follow the same rule.
> Are SHA-1 object names case insensitive too?
> 
> Case insensitivity has a history of being awkward. SMTP has always had
> case-insensitive commands, though the RFCs have always written them in
> upper case and implementations have pretty much all emitted them in upper
> case. See http://tools.ietf.org/html/rfc5321#section-2.4 especially the
> caveat about broken case-sensitive implementations.

There should be no problem with pkt-length being case insensitive, as standard conversion routines (strtol, sprintf) accept 0-9a-fA-F for base 16 / hexadecimal conversion. The requirement here is that client and server SHOULD use lowercase, but MUST accept mixed case (do case insensitive parsing of hex4).

I think SHA-1 is lowercased, so mixed case should work there. Well, at least "git show 6096D7" (note the uppercase 'D' in shortened SHA-1 name) works as expected.

But I do not know what are, or what should be protocol requirements. Should SHA-1 use lowercase, or be case insensitive? Should commands such as "have", "want", "done" use lower case or be case insensitive? Should status indicators "ACK" and "NAK" be upper case, or should be case insensitive? Should capabilities be case sensitive, and should they be compared case sensitive or not?

-- 
Jakub Narebski
Poland