Proposal: better library management ideas (was: how to checkout proper submodules)

Geoffrey Mainland mainland at
Mon Jun 10 13:08:18 CEST 2013

On 06/10/2013 11:49 AM, Nicolas Trangez wrote:
> On Mon, 2013-06-10 at 11:45 +0100, Ian Lynagh wrote:
>>> Side note: the fingerprint script *didn't even work* for almost
>>> a year after it was introduced; see commit 73ce2e70.
>> Which implies that wanting to go back in time is rare, so making it
>> easy
>> should be given low weight when considering the options?
> If 'git bisect' would work (out of the box) on the GHC repo, going back
> in time would certainly be a more common operation.

I agree. Going back in time is really, really hard with fingerprints
because you have to get the fingerprint files somewhere, and they don't
always exist.

Also, it could be the case that people used the fingerprint files to
"bisect" but didn't notice they weren't quite right because the
fingerprints were "close enough." OK for bug-finding, terrible for
reproduceable builds.

Many people on the list have been quite vocal about wanting to be able
to bisect. *I* have wanted to be able to bisect many, many times, but I
don't because it's such a pain.

I also want to be able to tell people how to build branches of ghc that
I am working on, e.g., the simd and th-new branches. That means having
to store a fingerprint file somewhere public and keep it in sync with my
tree. I would much rather just tell them to check out the foo branch of
ghc and be done with it.


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