[Nix-dev] Mirrors for fetchurl & Multiple versions

[Eelco Visser]

Hi Wouter,

Indeed! Both are problems that I've run into. Subversion is not
satisfactory for this versioning problem. The claim that Nix supports
multiple versions is vacuous if there is no model for keeping track of
versions;-)

-- Eelco

> I sometimes have problems with unavailable sources.
> 
> I think we should have the possibility to express mirrors:
> 
> fetchurl {
>                 urls = [ 
> ftp://freepascal.stack.nl/pub/fpc/dist/i386-linux-2.0.4/fpc-2.0.4.i386-linux.tar 
> 
>                             
> ftp://ftp.chg.ru/pub/lang/pascal/fpc/dist/i386-linux-2.0.4/fpc-2.0.4.i386-linux.tar 
> ];
>                 sha256 = 
> "0b2szv2anbf58h4i5mlph93afv9qdx6i0jqggba04d3anjbl9gfy";
> };
> 
> I thought that nix.cs.uu.nl mirrored all sources automatically, but i 
> seems not to do so always.
> 
> Second, sometimes I want to try an old version, but this is not easily 
> possible because we destructively overwrite Nix expressions. I can go 
> check SVN of course, but maybe we can expresses multiple versions in the 
> same expression. I know that some versions might require different 
> things, but maybe we can do something like this:
> 
> ----------------
> currentVersion = getVersion "2.0.6" versions
> 
> versions = [
> {              version = "2.0.4";
>                 urls = [ 
> ftp://freepascal.stack.nl/pub/fpc/dist/i386-linux-2.0.4/fpc-2.0.4.i386-linux.tar 
> 
>                             
> ftp://ftp.chg.ru/pub/lang/pascal/fpc/dist/i386-linux-2.0.4/fpc-2.0.4.i386-linux.tar 
> ];
>                 sha256 = 
> "0b2szv2anbf58h4i5mlph93afv9qdx6i0jqggba04d3anjbl9gfy";
> }
> {              version = "2.0.5";
>                 urls = [ 
> ftp://freepascal.stack.nl/pub/fpc/dist/i386-linux-2.0.4/fpc-2.0.5.i386-linux.tar 
> 
>                             
> ftp://ftp.chg.ru/pub/lang/pascal/fpc/dist/i386-linux-2.0.4/fpc-2.0.5.i386-linux.tar 
> ];
>                 sha256 = "xxxxxxxxxx";
> }
> {              version = "2.0.6";
>                 urls = [ 
> ftp://freepascal.stack.nl/pub/fpc/dist/i386-linux-2.0.4/fpc-2.0.6.i386-linux.tar 
> 
>                             
> ftp://ftp.chg.ru/pub/lang/pascal/fpc/dist/i386-linux-2.0.4/fpc-2.0.6.i386-linux.tar 
> ];
>                 sha256 = "xxxxxxxxxxx";
> } ];
> ----------------
> 
> and really destructively update or create new expressions when a new 
> version does need different things dependencies or patches.
> 
> So we would have 1 expression for sets of versions that work.
> 
> But on the other hand, it is verbose and maybe not going to be used 
> much, but maybe you have some thoughts on it.
> 
> Wouter
> 
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