Head broken again

[Manuel M T Chakravarty]

Simon Marlow wrote,
> Personally, I think requiring a complete bootstrap/testsuite on two 
> platforms for every patch is still prohibitively expensive: up to 2 
> hours for each build plus the time and effort to set them up - that's if 
> you even have access to 2 different platforms.  If the developer doesn't 
> have 2 platforms, then we have to do the testing.  What's the easiest 
> way to get the testing done?  Push the patch, and let buildbot do it.  
> This is why I think the staging/tested repositories suit our needs better.

I think its a matter of scalability.  The "testing by pushing to head" approach 
that you seem to advocate worked well enough when few people were hacking GHC. 
However, it seems that the number of GHC developers has been growing quite a bit 
in recent times - this includes an extension of the core team (ie, Igloo), 
contributions from SoC, etc.  With more patches to the head and more changes to 
core infrastructure, the head breaks more frequently.  As a result, more and 
more people waste their time with a broken head.  Even if we have the 
"guaranteed to be buildable" snapshots, there is an overhead in trying the head, 
discovering it is broken, and moving to a snapshot.

In any case, if this is the policy, I am no longer willing to perform our ndp 
development on a branch.  We did this so far to minimise disruption for others - 
although, most of our changes to GHC itself are isolated from mission critical 
components and are thus rather *unlikely* to break things for others (in 
contrast to all the build tree fiddling and the recent assembly/linker stuff).

Manuel