Re: [PATCH 00/11] Partial bundles

[Jeff Hostetler <git@jeffhostetler.com>]

On 2/28/22 12:54 PM, Derrick Stolee wrote:
> On 2/28/2022 12:00 PM, Jeff Hostetler wrote:
>> On 2/23/22 12:55 PM, Derrick Stolee via GitGitGadget wrote:
>>> While discussing bundle-URIs [1], it came to my attention that bundles have
>>> no way to specify an object filter, so bundles cannot be used with partial
>>> clones.
>>>
>>> [1]
>>> https://lore.kernel.org/git/7fab28bf-54e7-d0e9-110a-53fad6244cc9@gmail.com/
>>>
>>> This series provides a way to fix that by adding a 'filter' capability to
>>> the bundle file format and allowing one to create a partial bundle with 'git
>>> bundle create --filter=blob:none '.
>>
>> Nicely done.  There's a lot of refactoring here to move the
>> filtering code into a more usable place and get rid of some
>> of the awkward limitations of my original code.  Sorry that
>> you had to slog thru all of that.
>>
>>>
>>> There are a couple things that I want to point out about this implementation
>>> that could use some high-level feedback:
>>>
>>>    1. I moved the '--filter' parsing into setup_revisions() instead of adding
>>>       another place to parse it. This works for 'git bundle' but it also
>>>       allows it to be parsed successfully in commands such as 'git diff' which
>>>       doesn't make sense. Options such as '--objects' are already being parsed
>>>       there, and they don't make sense either, so I want some thoughts on
>>>       this.
>>
>> This feels like something that can wait for another task.
>> Let's keep this series focused on adding partial bundles.
> 
> What do you mean "can wait"? Do you recommend that I _don't_ do this
> refactor and instead implement filter parsing directly in bundles?
> 
> Or, are you saying that we should not worry about these potential
> side-effects of allowing (then ignoring) certain options in other
> commands, at least until a later series?

Sorry to be confusing here.  I just meant that the refactoring looks
good and we should continue with it.  And for now let's not worry
about those odd non-sense combinations that may now be possible.

That at some point later we can address the non-sense combinations
with some control flags on the call to the common parser or something.
I started thinking about that while looking at the code and just thought
that it would be a bit of a mess.  And that we didn't need to do any
thing about it now.  Such tweaking would be better done in a later
series.

>   
>>>    2. If someone uses 'git clone partial.bdl partial' where 'partial.bdl' is a
>>>       filtered bundle, then the clone will fail with a message such as
>>>
>>> fatal: missing blob object '9444604d515c0b162e37e59accd54a0bac50ed2e' fatal:
>>> remote did not send all necessary objects
>>>
>>> This might be fine. We don't expect users to clone partial bundles or fetch
>>> partial bundles into an unfiltered repo and these failures are expected. It
>>> is possible that we could put in custom logic to fail faster by reading the
>>> bundle header for a filter.
>>>
>>> Generally, the idea is to open this up as a potential way to bootstrap a
>>> clone of a partial clone using a set of precomputed partial bundles.
>>
>> I think this is to be expected.
>>
>> Would it help to have Git do a no-checkout clone when cloning
>> from a partial bundle?  Maybe that would give the user a chance to set
>> a real remote (and maybe set the partial clone/fetch config settings)
>> and then backfill their local clone??   (That might be functional, but
>> not very user-friendly....)
>>
>> Or should we just consider this limitation as a placeholder while we
>> wait for the Bundle URI effort?
> 
> It would be interesting to have another application of partial
> bundles, such as cloning directly from a bundle, then allowing
> a remote to be configured. It provides a "build-it-yourself"
> approach to bundle URIs for partial clones.
> 
> I'm not sure if such an application is required for this series,
> or if it could be delayed until after. I'm open to suggestions.

I think what you have here is nice and self-contained.  That is,
supporting partial bundles is a nice stop point.  Then have 1 or 2
series that consumes them.

Jeff