Re: [PATCH 1/5] pack-write: pass hash_algo to `fixup_pack_header_footer()`

[Junio C Hamano <gitster@pobox.com>]

Karthik Nayak via B4 Relay
<devnull+karthik.188.gmail.com@kernel.org> writes:

> From: Karthik Nayak <karthik.188@gmail.com>
>
> The `fixup_pack_header_footer()` function uses the global
> `the_hash_algo` variable to access the repository's hash function. To
> avoid global variable usage, pass the hash function from the layers
> above.
>
> Altough the layers above could have access to the hash function
> internally, simply pass in `the_hash_algo`. This avoids any
> compatibility issues and bubbles up global variable usage to upper
> layers which can be eventually resolved.

OK, so the aim is to make a bug-to-bug compatible rewrite at this
step.  We used to use the_hash_algo at the lowermost callee, so have
it take a hash_algo as parameter, but have everybody pass the_hash_algo
to it, even though a caller might have a more "suitable" hash_algo
for the data it is feeding the lower layer.

Which makes sense.

Naturally, as we are producing pack stream, we ought to have an idea
on what hash function is in use to name these objects in the pack
stream and the hash function used at the csum-file level, so all
callers ought to have the information eventually (and if some of
them are relying on the_hash_algo currently, they need to be fixed).
All of that can be left for some future date and blindly passing
down the_hash_algo from all callers in this patch is a good approach
to establish a solid foundation to build on.