Re: [rfc] flip rerere.enabled default to be "on" at Git 3.0 boundary?

From: Ben Knoble <ben.knoble@gmail.com>
Date: Oct 22, 2025, 17:45 UTC
Message-ID: <80220653-7302-4E4D-99E9-1A8CB5B4F23D@gmail.com>
In-Reply-To: <bec27479-c53f-472c-87c7-374321108ad5@kdbg.org>

Show 30 quoted lines

> Le 22 oct. 2025 à 01:55, Johannes Sixt <j6t@kdbg.org> a écrit :
> 
> Am 21.10.25 um 20:55 schrieb Kristoffer Haugsbakk:
>>> On Tue, Oct 21, 2025, at 20:21, Junio C Hamano wrote:
>>> A good default matters, and people who find out how useful a rerere
>>> database is would say "gee, that sounds great but why they do not
>>> enable it by default?  It is too buggy and they wanted to reduce the
>>> number of support requests?"  Yes, the reason it is not enabled by
>>> default initially was exactly that, i.e. those opt into the feature
>>> was used as guinea pigs to polish the feature.  But we forgot to set
>>> the graduation criteria and never said "ok it is mature enough, so
>>> let's turn it on for everybody".
>>> 
>>> Perhaps Git 3.0 boundary is a good occasion to do so?
>> 
>> This sounds nice.
> 
> While I agree that the rerere cache is a very valuable tool to have, it
> has the very sharp edge that a cached wrong resolution is extremely
> difficult to get rid of.
> 
> Merge conflicts and how to resolve them correctly is a skill that needs
> to be trained. Giving a novice who is still tipping their toes into the
> waters of merge resolution the advice to "just enable rerere" exposes
> them to a behavior whose results (the reuse of incorrect merge
> resolutions that they thought they had already corrected) are
> inexplicable without the help of an expert.
> 
> I think I'm saying that I am mildly opposed to enable rerere by default
> as long as it has this sharp edge.

Fair points. Could I ask an enterprising reader to summarize the sharp edges of rerere that need polished? It could make an effective todo list to aim for prior to 3.0. Here’s what I recall seeing:
- messaging is not clear
- usage for dealing with incorrect caches needs improvement (should be useable without expert intervention)
    - as a first step, perhaps having rerere and status display more information about possible steps to take (review results, keep or discard) would help?