Subject: Re: [PATCH/RFC] send-pack.c: Allow to disable side-band-64k

From: Thomas Braun <[email-masked]>
Date: Mon, 19 May 2014 23:15:00 +0200

Am 19.05.2014 21:33, schrieb Jonathan Nieder:
> Hi,
>
> Thomas Braun wrote:
>
>> pushing over the dump git protocol with a windows git client.
>
> I've never heard of the dump git protocol.  Do you mean the git
> protocol that's used with git:// URLs?

You are right I mean the protocol involving git:// URLs. But 
unfortunately I got it wrong as according to [1] the git:// is one of 
the so-called smart protocols. That was also the source where I read 
that there are smart and dump protocols.

[1]: http://git-scm.com/book/en/Git-Internals-Transfer-Protocols

> [...]
>> Alternative approaches considered but deemed too invasive:
>> - Rewrite read/write wrappers in mingw.c in order to distinguish between
>>    a file descriptor which has a socket behind and a file descriptor
>>    which has a file behind.
>
> I assume here "too invasive" means "too much engineering effort"?
>
> It sounds like a clean fix, not too invasive at all.  But I can
> understand wanting a stopgap in the meantime.

No actually I meant too invasive in the sense of "requiring large 
rewrites which only benefit git on windows and hurt all others".

The two fixes I can think of either involve:
- In a read *and* write wrapper the need to check if the fd is a socket, 
if yes use send/recv if no use read/write. According to Erik's comments 
this should be possible. But I would deem the expected performance 
penalty quite large as that will be done in every call.
- Rewriting read/write to accept windows handles instead of file 
descriptors. Only a theoretical option IMHO.

For me the goal is also to minimise the diff between git and msysgit/git.

>
>> - Turning the capability side-band-64k off completely. This would remove a useful
>>    feature for users of non-affected transport protocols.
>
> Would it make sense to turn off sideband unconditionally on Windows
> when using the relevant protocols?
>

Yes, if this would be also acceptable for git.git.

I can check at the call site of send_pack in transport.c what protocol 
is in use, and then pass a new parameter use_sideband to it.
Or maybe "adapt" server_capabilities in connect.c to not include 
side-band-64k if using git:// ?

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