Re: [RFC v3] cat-file: add a --stdin-cmd mode

From: John Cai <johncai86@gmail.com>
Date: Feb 1, 2022, 19:27 UTC
Message-ID: <674CD40F-7060-4892-97CD-1940AEF7C3D7@gmail.com>
In-Reply-To: <YflzZsb/txsopusP@nand.local>

Hi Taylor,

On 1 Feb 2022, at 12:52, Taylor Blau wrote:

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> On Tue, Feb 01, 2022 at 10:39:30AM +0100, Christian Couder wrote:
>> Also I think at this point this should probably not be an RFC patch
>> anymore but a regular one.
>
> I think that this is due to my first "review" in [1], where I tried to
> get an understanding of what John's concrete usage plans were, since I
> couldn't figure out what they were on my own.
>
> I'm not sure that I've seen a response along the lines of "we need to
> control when the output stream is flushed in order to do ..." yet, but I
> would be interested to see one before moving too much further ahead of
> where we already are.

This would be useful when there is another process A interacting with a long running git cat-file process B that is retrieving object information from the odb interactively but also wants to use --buffer mode.

In this scenario, if A is asked to retrieve a large list of object metadata, it wants to use --buffer mode to be more efficient but it would need a way to ensure that all of the contents have been flushed to the output. If we want to keep B running to save startup time (since otherwise we might need to spawn many git cat-file processes), then having a flush command where we can guarantee a flush would be very handy.

>
> (Apologies if such a response was written, and I missed it).

Nope, don't think I explained the need for a flush command very clearly.

thanks

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>
> Thanks,
> Taylor
>
> [1]: https://lore.kernel.org/git/YehomwNiIs0l83W7@nand.local/