The major difference between switch and roots is that remotes are shared across 
switches. Pins are already per-switch.

There's a good case to be made for a per-project OPAM installation, especially 
for OCaml applications that just want to build a binary with the minimum hassle 
(such as Facebook's Flow static analyser).  See here for a discussion on the 
topic:
https://github.com/ocaml/opam/issues/1372 
<https://github.com/ocaml/opam/issues/1372>

I'd quite like to see an `opam-local` script as discussed in that issue.  It 
should be a lot easier now that OPAM 1.2 has been released.

-anil

> On 26 Jan 2015, at 20:58, Gabriel Scherer <[email protected]> wrote:
> 
> Dear opam-devel,
> 
> Guillaume Claret (one of the Coq developpers) has been experimenting with 
> using one OPAM root for each of his software projects, instead of using 
> global switches.
> 
>   http://coq-blog.clarus.me/use-opam-for-coq.html 
> <http://coq-blog.clarus.me/use-opam-for-coq.html>
> 
> I have a personal preference for keeping using switches that I'm familiar 
> with and seem more idiomatic in OCaml usage (and also compiling Coq in each 
> project would remind me too much of my Gentoo years), but Guillaume points 
> out that it has evolved to be standard usage in the Node/npm community (and 
> with Python/virtualenv I think), and that it can solve incompatible-version 
> headaches by having a finer granularity. More generally the rationale seems 
> to be "local is better than global", which sounds reasonable.
> 
> (Besides compilation time and duplication of efforts -- that could be 
> partially solved if/when binary packages where to see the light -- a good 
> argument in favor of switches would be the ability to install programs across 
> multiple switches in the same root, eg. opam compiler-conf and similiar 
> scripts.)
> 
> Do you know of other users having converged towards that per-project scheme? 
> Is there tool support, or interest in eventually supporting, for this mode of 
> use in upstream OPAM?
> _______________________________________________
> opam-devel mailing list
> [email protected]
> http://lists.ocaml.org/listinfo/opam-devel

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