If --no-build-output is given (which will become the default for the
"nix" command at least), show the last 10 lines of the build output if
the build fails.
This replaces nix-push. For example,
$ nix copy --to file:///tmp/cache -r $(type -p firefox)
copies the closure of firefox to the specified binary cache. And
$ nix copy --from file:///tmp/cache --to s3://my-cache /nix/store/abcd...
copies between two binary caches.
It will also replace nix-copy-closure, once we have an SSHStore class,
e.g.
$ nix copy --from ssh://alice@machine /nix/store/abcd...
This allows commands like "nix verify --all" or "nix path-info --all"
to work on S3 caches.
Unfortunately, this requires some ugly hackery: when querying the
contents of the bucket, we don't want to have to read every .narinfo
file. But the S3 bucket keys only include the hash part of each store
path, not the name part. So as a special exception
queryAllValidPaths() can now return store paths *without* the name
part, and queryPathInfo() accepts such store paths (returning a
ValidPathInfo object containing the full name).
Caching path info is generally useful. For instance, it speeds up "nix
path-info -rS /run/current-system" (i.e. showing the closure sizes of
all paths in the closure of the current system) from 5.6s to 0.15s.
This also eliminates some APIs like Store::queryDeriver() and
Store::queryReferences().
"verify-store" is now simply an "--all" flag to "nix verify". This
flag can be used for any other store path command as well (e.g. "nix
path-info", "nix copy-sigs", ...).
For convenience, you can now say
$ nix-env -f channel:nixos-16.03 -iA hello
instead of
$ nix-env -f https://nixos.org/channels/nixos-16.03/nixexprs.tar.xz -iA hello
Similarly,
$ nix-shell -I channel:nixpkgs-unstable -p hello
$ nix-build channel:nixos-15.09 -A hello
Abstracting over the NixOS/Nixpkgs channels location also allows us to
use a more efficient transport (e.g. Git) in the future.
Thus, -I / $NIX_PATH entries are now downloaded only when they are
needed for evaluation. An error to download an entry is a non-fatal
warning (just like non-existant paths).
This does change the semantics of builtins.nixPath, which now returns
the original, rather than resulting path. E.g., before we had
[ { path = "/nix/store/hgm3yxf1lrrwa3z14zpqaj5p9vs0qklk-nixexprs.tar.xz"; prefix = "nixpkgs"; } ... ]
but now
[ { path = "https://nixos.org/channels/nixos-16.03/nixexprs.tar.xz"; prefix = "nixpkgs"; } ... ]
Fixes#792.
Just wasted a couple hours chasing shadows because the nix store got
corrupted and there was no indication of that anywhere.
Since an install is one-time only, might as well verify. Optimization
showed that the copied files aren't read-only; fixed that as well.
Also, use /bin/sh since there's a good chance that this script will be
run on systems without /bin/bash
