E.g.
$ nix-build -I nixpkgs=git://github.com/NixOS/nixpkgs '<nixpkgs>' -A hello
This is not extremely useful yet because you can't specify a
branch/revision.
The function builtins.fetchgit fetches Git repositories at evaluation
time, similar to builtins.fetchTarball. (Perhaps the name should be
changed, being confusing with respect to Nixpkgs's fetchgit function,
with works at build time.)
Example:
(import (builtins.fetchgit git://github.com/NixOS/nixpkgs) {}).hello
or
(import (builtins.fetchgit {
url = git://github.com/NixOS/nixpkgs-channels;
rev = "nixos-16.03";
}) {}).hello
Note that the result does not contain a .git directory.
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().
