[darcs-users] new GHC support policy draft

Eric Kow kowey at darcs.net
Thu Mar 18 13:39:37 UTC 2010

Hi everybody,

Below is the second draft of our GHC version support, hopefully taking
in account points raised by everybody.

It appears to be a balancing act: for users, it's sometimes important to
run new Darcs on servers; for developers trying to support too many GHC
versions is problematic.  This new policy leans slightly more towards
the developer end [the better to server users!] but introduces new
safeguards to compensate.

If there are no serious objections to this, I'd like to enshrine this on
the wiki as our new policy :-)


Thanks for all the comments!


Things we have to consider
* Support here means ensuring that Darcs build on this (buildbots)
  and also accepting bugs for Darcs built against these versions

* Users to support:

  - MacOS X / Windows: I think the latest Haskell Platform is a
    safe bet here
  - Folks on Desktop Linux: Recent but not bleeding edge GHC
    The 6-monthly distributions like Fedora and Ubuntu are a
    good guide here
  - Folks on Servers: Old GHC not often available through

* Changes in GHC make supporting many versions of GHC extremely
  inconvenient, which impairs our ability to make Darcs better

* Supporting many versions of GHC is also potentially unsafe, as
  it leaves the door open to many untested ways of building Darcs.

The policy
1. We will support the last two stable branches of GHC.

   Tying this to the GHC and not to any particular distribution
   makes the number of GHC versions we promise to support a fixed
   quantity.  This keeps Darcs hackers sane so they can focus on
   hacking Darcs.

2. We will provide a human-readable recipe for installing Darcs on the
   current Debian Stable on http://wiki.darcs.net/Debian.  We choose
   Debian Stable simply because it's a good guide for what people
   running servers can be expected to have.
   Before we jettison a GHC version, we will first ensure that a non
   Darcs hacker can use the recipe to successfully install Darcs.  We
   will also try to make this procedure as simple and convenient as
   possible.  For example, we could write it in a way that prefers in

    - what Debian Stable provides
    - what Debian backports provide
    - the GHC bindist
    - source tarballs

Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow>
PGP Key ID: 08AC04F9
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