Storing serialised graph along with packages

[Ricardo Wurmus]

Hey Guix,

it always bothered me that after building a package we lose all of the
beautiful features that Guix as a Guile library gives us.  We always
need to keep track of the Guix version at the time of building the
package and only then can we hope to rebuild the same thing again at
some point in the future.

What do you think about storing the serialised subset of the package
graph in a separate output of the package?  Currently, the only place
where we store anything meta is the database.  Wouldn’t it be great if
we could “dump an image” of the state of Guile when it has evaluated the
section of the package graph that is needed to build it?

Then we could just load the serialised state into Guile at a later point
and inspect the package graph as if we had Guix checked out at the given
version.  I suppose we could also store this kind of information in the
database.

I’d really like the graph to stay alive even after Guix has moved on to
later versions.  It also sounds like a really lispy thing to do.

What do you think?

--
Ricardo

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