Coordinating the Hadrian merge

[Alp Mestanogullari]

Hello,

Andrey: the hadrian submodule has been around for a while now, yet 
people have not exactly abandoned the make build system. Merging hadrian 
in the main ghc repo just means turning that submodule into a proper 
subdirectory, after all. I might be wrong but I really doubt this will 
make much of a difference for most ghc devs and suddenly catch 
everyone's attention.

The most important point of merging, in my opinion, once we "unbreak" 
hadrian, will be to add at least one hadrian job in CI to make sure that 
this (breakage) never happens without us noticing right away, so ideally 
before differentials land.

I don't see the merge as "alright, hadrian's ready, let's use it 
everyone", it's really about us hadrian contributors not finding the 
"catch-up" game all that fun after we've played it dozens of times. 
Without all those bumps on the road, who knows where hadrian would be 
right now.

On 16/10/2018 01:12, Andrey Mokhov wrote:
> Hi Ben,
>
> Yes, I'm fine to merge, but we should make it clear that Hadrian should not be used just yet:
>
> 1) It is currently broken due to some recent changes in GHC.
>
> 2) Alp made tremendous progress with fixing the testsuite failures, but there are still some failures left.
>
> 3) There are a few usability requests by Simon Marlow that we need to address.
>
>> In the past we discussed squashing the project's early history
>> however I've had very little luck doing this cleanly
> Ouch, it would be a bit grim to merge all those early commits. On the other hand, I looked at commits at the middle of Hadrian's history and they look quite sensible, just overly fine-grained. So, even if we could somehow squash the early history, that probably wouldn't give us much saving in terms of the commit count -- it would still be more than 1K.
>
> P.S.: Don't forget to switch off commit notifications when you do the merge ;-)
>
> Cheers,
> Andrey
>
> -----Original Message-----
> From: Ben Gamari [mailto:ben at well-typed.com]
> Sent: 15 October 2018 23:14
> To: Andrey Mokhov <andrey.mokhov at newcastle.ac.uk>; Alp Mestanogullari <alp at well-typed.com>
> Cc: GHC developers <ghc-devs at haskell.org>
> Subject: Coordinating the Hadrian merge
>
> Hi Andrey and Alp,
>
> Before ICFP we concluded that we will merge Hadrian into the GHC tree.
> This unfortunately took a back-seat priority-wise while I sorted out
> various release things but I think we are now in a position to make this
> happen.
>
> Andrey, would you be okay with my merging Hadrian as-is into the GHC
> tree? In the past we discussed squashing the project's early history
> however I've had very little luck doing this cleanly (primarily due to
> the difficulty of rebasing in the presence of merge commits)
>
> After merging there will be a period where we flush the pull request
> queue but I don't anticipate this causing much trouble.
>
> Cheers,
>
> - Ben
>

-- 
Alp Mestanogullari, Haskell Consultant
Well-Typed LLP, https://www.well-typed.com/

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