These are all symlinks to 'nix' now, reducing the installed size by
about ~1.7 MiB.

This allows commands like

nix build --log-lines 30 nixpkgs.hello

in order to obtain more information in case of a failure.

In structured-attributes derivations, you can now specify per-output
checks such as:

  outputChecks."out" = {
    # The closure of 'out' must not be larger than 256 MiB.
    maxClosureSize = 256 * 1024 * 1024;

    # It must not refer to C compiler or to the 'dev' output.
    disallowedRequisites = [ stdenv.cc "dev" ];
  };

  outputChecks."dev" = {
    # The 'dev' output must not be larger than 128 KiB.
    maxSize = 128 * 1024;
  };

Also fixed a bug in allowedRequisites that caused it to ignore
self-references.

The `--graphml` option can be used instead.

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

  $ nix-store -qR /nix/store/fnord
  nix-store: src/libstore/store-api.cc:80: std::__cxx11::string nix::storePathToHash(const Path&): Assertion `base.size() >= storePathHashLen' failed.
  Aborted

Fixes #2075.

Since its superclass RemoteStore::Connection contains 'to' and 'from'
fields that refer to the file descriptor maintained in the subclass,
it was possible for the flush() call in Connection::~Connection() to
write to a closed file descriptor (or worse, a file descriptor now
referencing another file). So make sure that the file descriptor
survives 'to' and 'from'.

For example, this prevents a "kvm" build on machines that don't have
KVM.

Fixes #2012.

This is primarily because Derivation::{can,will}BuildLocally() depends
on attributes like preferLocalBuild and requiredSystemFeatures, but it
can't handle them properly because it doesn't have access to the
structured attributes.

E.g. __noChroot and allowedReferences now work correctly. We also now
check that the attribute type is correct. For instance, instead of

  allowedReferences = "out";

you have to write

  allowedReferences = [ "out" ];

Fixes #2453.

This meant that making a typo in an s3:// URI would cause a bucket to
be created. Also it didn't handle eventual consistency very well. Now
it's up to the user to create the bucket.

Tools which re-exec `$SHELL` or `$0` or `basename $SHELL` or even just
`bash` will otherwise  get the non-interactive bash, providing a
broken shell for the same reasons described in
https://github.com/NixOS/nixpkgs/issues/27493.

Extends c94f3d55

Presumably this refers to ./default.nix but the support for that in
'nix' is tenuous. Also folders are a Mac thing.

* Don't wait forever for the client to remove data from the
  buffer. This does mean that the buffer can grow without bounds
  (e.g. when downloading is faster than writing to disk), but meh.

* Don't hold the state lock while calling the sink. The sink could
  take any amount of time to process the data (in particular when it's
  actually a coroutine), so we don't want to block the download
  thread.

In particular this causes copyStorePath() from HttpBinaryCacheStore to
only start a download if needed. E.g. if the destination LocalStore
goes to sleep waiting for the path lock and another process creates
the path, then LocalStore::addToStore() will never read from the
source so we don't have to do the download.

Changes

  std::bad_alloc

into

  bad archive: input doesn't look like a Nix archive

(cherry picked from commit a94a2eb1cb1c81e90a7529be5fecac27899a3442)

Fixes #2425.

Otherwise, we just keep asking the substituter for other .narinfo
files, which can take a very long time due to retries/timeouts.

Fixes #1990.

We shouldn't pollute stdout.

Fixes #2393.

‘geteuid’ gives us the user that the command is being run as,
including in setuid modes. By using geteuid to determind id, we can
avoid the ‘sudo -i’ hack when upgrading Nix. So now, upgrading Nix on
macOS is as simple as:

$ sudo nix-channel --update
$ sudo nix-env -u

$ sudo launchctl stop org.nixos.nix-daemon
$ sudo launchctl start org.nixos.nix-daemon
or
$ sudo systemctl restart nix-daemon

This is already done by coerceToString(), provided that the argument
is a path (e.g. 'fetchGit ./bla'). It fixes the handling of URLs like
git@github.com:owner/repo.git. It breaks 'fetchGit "./bla"', but that
was never intended to work anyway and is inconsistent with other
builtin functions (e.g. 'readFile "./bla"' fails).

Fixes #2390.