[opam-devel] How to manage a package manager (Was: Re: [opam] Build clarification (#1149))

[Anil Madhavapeddy]

On 31 Jan 2014, at 17:28, Roberto Di Cosmo <roberto at dicosmo.org> wrote:

>     I am a bit unhappy with the current state of affairs, where new
>     versions of opam appear with incompatible changes in the repository format,
>     hence different versions of the repositories: people using old versions
>     of opam get lost in a limbo-like repository with non updated packages
>     until they realise they need to recompile a new version of opam
>     to see the light again.

To be clear, the reason for OPAM 1.0 to 1.1 being incompatible was "unplanned".  The original release was too strict with it's parsing, and OPAM 1.1 is now far more lax.

There's also support for the 'repo' file already (in both OPAM 1.0 and 1.1) which allow redirections (as happens with 1.0->1.1).

All-in-all, we're in pretty good shape for upgrades.  Some features such as multiple archive support need some thought, since changing the type of field could be tricky, but it's not impossible to maintain backwards compatibility.

-anil