Building ghc on Windows with msys2

[cg]

On 10/8/2014 1:03 AM, Austin Seipp wrote:
>>
>> I hide 'empty' and 'foldr' at importing point and the code compiles.
>>
>> Has anyone see the same issues?
>
> Ugh, this is some fallout I thought we had fixed, but apparently not.
> I'll fix it shortly, thanks.
>
[...]
>>
>> Why does ghc-stage1.exe use so much memory?
>
> Wow, I thought we fixed this one too! Please see this bug:
>
> https://ghc.haskell.org/trac/ghc/ticket/9630
>
> What GHC commit are you using? Are your submodules all up to date? In
> particular, if 'binary' is not up to date, even if the rest of your
> tree is, you'll see this problem.
>

Ah, I know what causes the building failure now...

After cloning ghc repository, I switch every sub-module to Master (it is
usually HEAD) branch.

I am in the habit of thinking Master is always the latest.

But it is not the case with ghc. For example, the fix mentioned in 
ticket 9630
was submitted to ghc-head branch[1], but the Master/HEAD is way old[2].

And it seems there is some other submodule is like this.

Now after cloning ghc repository, if I don't switch to any branch -- 
'git branch'
will show all submodules are detached -- the build will succeed.

So why the Master/HEAD branches don't have the latest code?

Thanks,
cg

[1] http://git.haskell.org/packages/binary.git/log/refs/heads/ghc-head
[2] http://git.haskell.org/packages/binary.git/log/refs/heads/master