This reverts commit f78126bf. There
really is no need for such a massive change...

This unbreaks "nixos-rebuild --upgrade".

Fixes #1135.

Fixes #1132

This cuts hydra-queue-runner's peak memory usage by about a third.

buildPaths() on a non-derivation would incorrectly not throw an error
if the path didn't have a substitute.

This solves a problem whereby if /gnu/store/.links had enough entries,
ext4's directory index would be full, leading to link(2) returning
ENOSPC.

* nix/libstore/optimise-store.cc (LocalStore::optimisePath_): Upon
ENOSPC from link(2), print a message and return instead of throwing a
'SysError'.

Fix comments parsing

Fixed the parsing of multiline strings ending with an even number of
stars, like /** this **/.
Added test cases for comments.

This way, callers can exploits the parallelism of computeFSClosure()
when they have multiple paths that they need the (combined) closure of.

Needed by Hydra.

The SSHStore PR adds this functionality to the daemon, but we have to
handle the case where the Nix daemon is 1.11.

Also, don't require signatures for trusted users. This restores 1.11
behaviour.

Fixes https://github.com/NixOS/hydra/issues/398.

The current behaviour modifies the first writeable file from amongst
.bash_profile, .bash_login and .profile.  So .bash_profile (if it is
writable) would be modified even if a user has already sourced nix.sh
in, say, .profile.

This commit introduces a new environment variable,
NIX_INSTALLER_NO_MODIFY_PROFILE.  If this is set during installation,
then the modifications are unconditionally skipped.

This is useful for users who have a manually curated set of dotfiles
that they are porting to a new machine. In such scenarios, nix.sh is
already sourced at a place where the user prefers.  Without this
change, the nix installer would insist on modifying .bash_profile if
it exists.

This commit also add documentations for both the current behaviour and
the new override.

For example, you can now set

  build-sandbox-paths = /dev/nvidiactl?

to specify that /dev/nvidiactl should only be mounted in the sandbox
if it exists in the host filesystem. This is useful e.g. for EC2
images that should support both CUDA and non-CUDA instances.

Fixes #1084

Fix SIGFPE from integer overflow during division

On some architectures (like x86_64 or i686, but not ARM for example)
overflow during integer division causes a crash due to SIGFPE.
Reproduces on a 64-bit system with:

    nix-instantiate --eval -E '(-9223372036854775807 - 1) / -1'

The only way this can happen is when the smallest possible integer is
divided by -1, so just special-case that.

The removal of CachedFailure caused the value of TimedOut to change,
which broke timed-out handling in Hydra (so timed-out builds would
show up as "aborted" and would be retried, e.g. at
http://hydra.nixos.org/build/42537427).

The store parameter "write-nar-listing=1" will cause BinaryCacheStore
to write a file ‘<store-hash>.ls.xz’ for each ‘<store-hash>.narinfo’
added to the binary cache. This file contains an XZ-compressed JSON
file describing the contents of the NAR, excluding the contents of
regular files.

E.g.

  {
    "version": 1,
    "root": {
      "type": "directory",
      "entries": {
        "lib": {
          "type": "directory",
          "entries": {
            "Mcrt1.o": {
              "type": "regular",
              "size": 1288
            },
            "Scrt1.o": {
              "type": "regular",
              "size": 3920
            },
          }
        }
      }
      ...
    }
  }

(The actual file has no indentation.)

This is intended to speed up the NixOS channels programs index
generator [1], since fetching gazillions of large NARs from
cache.nixos.org is currently a bottleneck for updating the regular
(non-small) channel.

[1] https://github.com/NixOS/nixos-channel-scripts/blob/master/generate-programs-index.cc

Done slightly differently from https://github.com/NixOS/nix/pull/1093.

This caused the gc test to fail on Darwin.

.gitignore: catch up with perl -> c conversion