Inside a derivation, exportReferencesGraph already provides a way to
dump the Nix database for a specific closure. On the command line,
--dump-db gave us the same information, but only for the entire Nix
database at once.
With this change, one can now pass a list of paths to --dump-db to get
the Nix database dumped for just those paths. (The user is responsible
for ensuring this is a closure, like for --export).
Among other things, this is useful for deploying a closure to a new
host without using --import/--export; one can use tar to transfer the
store paths, and --dump-db/--load-db to transfer the validity
information. This is useful if the new host doesn't actually have Nix
yet, and the closure that is being deployed itself contains Nix.
This prints the references graph of the store paths in the graphML
format [1]. The graphML format is supported by several graph tools
such as the Python Networkx library or the Apache Thinkerpop project.
[1] http://graphml.graphdrawing.org
In particular, drop the "build-" and "gc-" prefixes which are
pointless. So now you can say
nix build --no-sandbox
instead of
nix build --no-build-use-sandbox
This allows various Store implementations to provide different ways to
get build logs. For example, BinaryCacheStore can get the build logs
from the binary cache.
Also, remove the log-servers option since we can use substituters for
this.
