sharing package directories (i.e., the result of building a Nix
descriptor).
`nix-pull-prebuilts' obtains a list of all known prebuilts by
consulting the paths and URLs specified in
$prefix/etc/nix/prebuilts.conf. The mappings ($pkghash,
$prebuilthash) and ($prebuilthash, $location) are registered with
Nix so that it can use the prebuilt with hash $prebuilthash when
installing a package with hash $pkghash by downloading and unpacking
$location.
`nix-push-prebuilts' creates prebuilts for all packages for which no
prebuilt is known to exist. It can then optionally upload these
to the network through rsync.
`nix-[pull|push]-prebuilts' just provide a policy. Nix provides the
mechanism through the `nix [export|regprebuilt|regurl]' commands.
* Conditionals and variables in Fix expressions. This allows, e.g.,
Descr(
[ Bind("pkgId", "subversion-0.21.0")
, Bind("httpsClient", Bool(True))
, Bind("httpServer", Bool(True))
, Bind("ssl", If(Var("httpsClient"), Fix("./openssl-0.9.7b.fix"), ""))
, Bind("httpd", If(Var("httpServer"), Fix("./httpd-2.0.45.fix"), ""))
...
])
which introduces domain feature variables httpsClient and httpServer
(i.e., whether Subversion is built with https client and webdav
server support); the values of the variables influences package
dependencies and the build scripts.
The next step is to allow that packages can express constraints on
each other. E.g., StrategoXT is dependent on an ATerm library with
the "gcc" variant enabled. In fact, this may cause several
Nix instantiations to be created from a single Fix descriptor. If
possible, Fix should try to find the least set of instantiations
that obeys the constraints.
descriptors generated out of Fix descriptors specified on the
command line. This allows us to say:
nix-switch $(fix -i ./test/fixdescriptors/system.fix)
