[darcs-devel] [issue589] Impossible case in darcs PatchRead.lhs or Patch/Read.lhs

[Michael Abbott]

> Michael, could this download be passing through a proxy that might 
> modify the files?
>
> Could you diff the contents of your _darcs/patches directory agains that of the
> attached yi.tar.bz2?

Absolute, and this was definitely the trigger.  It took me a while to 
figure it out (there are some 1,500 patches in Yi) but, yes, for whatever 
reason our web poxy decided to transform one patch into something 
completely different.

So perhaps this transforms the issue from an outright bug into an 
unfriendly behaviour.  I see two points:

1. The error message implies that the problem is entirely the fault of 
darcs (and so of course gives little hint about identifying the true 
culprit).

2. Evidently darcs fails to do any checking on the patches before 
processing them.  A CRC checksum might be a good thing.

Actually, the fact that darcs fetchs each of 1500 patches as separate http 
requests is itself rather painful: takes much longer than it would if this 
could be done as a single http or https request -- and using https would 
bypass any brain damaged proxy to further benefit!