On 2/1/2018 1:57 PM, Stefan Beller wrote:

On Thu, Feb 1, 2018 at 10:48 AM, Jeff Hostetler [off-list ref] wrote:

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On 1/2/2018 7:18 PM, Brandon Williams wrote:

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Introduce git-serve, the base server for protocol version 2.

[...]

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+ Special Packets
+-----------------
+
+In protocol v2 these special packets will have the following semantics:
+
+  * '0000' Flush Packet (flush-pkt) - indicates the end of a message
+  * '0001' Delimiter Packet (delim-pkt) - separates sections of a message

Previously, a 0001 pkt-line meant that there was 1 byte of data
following, right?

No, the length was including the length field, so 0005 would indicate that
there is one byte following, (+4 bytes of "0005" included)

d'oh.  right.  thanks!

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Should we also consider increasing the pkt-line limit to 5 hex-digits
while we're at it ?   That would let us have 1MB buffers if that would
help with large packfiles.

AFAICT there is a static allocation of one pkt-line (of maximum size),
such that the code can read in a full packet and then process it.
If we'd increase the packet size we'd need the static buffer to be 1MB,
which sounds good for my developer machine. But I suspect it may be
too much for people using git on embedded devices?

I got burned by that static buffer once upon a time when I wanted
to have 2 streams going at the same time.  Hopefully, we can move
that into the new reader structure at some point (if it isn't already).

pack files larger than 64k are put into multiple pkt-lines, which is
not a big deal, as the overhead of 4bytes per 64k is negligible.
(also there is progress information in the side channel, which
would come in as a special packet in between real packets,
such that every 64k transmitted you can update your progress
meter; Not sure I feel strongly on fewer progress updates)

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  Granted, we're throttled by the network,
so it might not matter.  Would it be interesting to have a 5 digit
prefix with parts of the high bits of first digit being flags ?
Or is this too radical of a change?

What would the flags be for?

As an alternative we could put the channel number in one byte,
such that we can have a side channel not just while streaming the
pack but all the time. (Again, not sure if that buys a lot for us)

Delimiters like the 0001 and the side channel are a couple of
ideas, but I was just thinking out loud.  And right, I'm not sure
it gets us much right now.

Jeff