Nix sometimes outputs a warning message like this:
```
directory /nix does not exist; creating it by running ‘?? using sudo
```
... when it really meant to output something that looked like this:
```
directory /nix does not exist; creating it by running 'mkdir -m 0755 /nix && chown gabriel /nix' using sudo
```
The reason why is due to some bizarre behavior in Bash where it will translate anything of the form `$x’` to `??`, leading to the incorrect warning message. I don't know what is the origin of this Bash behavior, but the easiest fix is to just use ASCII quotes instead of unicode quotes.
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.
The existing "nix-build" examples were failing:
error: cannot auto-call a function that has an argument without a default value (‘system’)
Thanks to @groxxda on irc for pointing out the fix!
Updated to completely remove unneeded path argument, suggested by @joachifm
Updated to remove other occurences of `all-packages.nix` from files as
suggested by @domenkozar
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...
