Re: [PATCH v2 1/2] maintenance: set log.excludeDecoration durin prefetch

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

"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Derrick Stolee <dstolee@microsoft.com>
>
> The 'prefetch' task fetches refs from all remotes and places them in the
> refs/prefetch/<remote>/ refspace. As this task is intended to run in the
> background, this allows users to keep their local data very close to the
> remote servers' data while not updating the users' understanding of the
> remote refs in refs/remotes/<remote>/.
>
> However, this can clutter 'git log' decorations with copies of the refs
> with the full name 'refs/prefetch/<remote>/<branch>'.
>
> The log.excludeDecoration config option was added in a6be5e67 (log: add
> log.excludeDecoration config option, 2020-05-16) for exactly this
> purpose.
>
> Ensure we set this only for users that would benefit from it by
> assigning it at the beginning of the prefetch task. Other alternatives
> would be during 'git maintenance register' or 'git maintenance start',
> but those might assign the config even when the prefetch task is
> disabled by existing config. Further, users could run 'git maintenance
> run --task=prefetch' using their own scripting or scheduling. This
> provides the best coverage to automatically update the config when
> valuable.

OK.  I think those users who keep distance from "git maintenance"
are different story but all others cannot be using refs/prefetch/
hierarchy for purposes other than "git maintenance" dictates, so
"git maintenance [register|start]", or even when the user first runs
"git maintenance" for that matter, would be acceptable point to add
the configuration, but at the beginning of a prefetch task, we know
the hierarchy is being used for what "git maintenance" wants to do,
so it is a good place to do so.

But playing devil's advocate, I do not think throwing refs/prefetch
into a "hardcoded list of hierarchies that would never be used for
decoration purposes" would upset any end-users in practice.  The only
reason why I do not make such a suggestion is it is more work (such
a hardcoded reject list does not exist, if I recall correctly).

> It is improbable, but possible, that users might want to run the
> prefetch task _and_ see these refs in their log decorations. This seems
> incredibly unlikely to me, but users can always opt-in on a
> command-by-command basis using --decorate-refs=refs/prefetch/.

It is not a viable workaround to add "--decorate-refs=refs/prefetch"
that is a mouthful; configuration options are to reduce such typing,
not to force more of them.  But because I agree with that
"incredibly unlikely" assessment, I do not care.

Thanks.