- rename options but leav old names as lower-priority aliases,
  also "-dirs" -> "-paths" to get closer to the meaning
- update docs to reflect the new names (old aliases are not documented),
  including a new file with release notes
- tests need an update after corresponding changes to nixpkgs
- __noChroot is left as it is (after discussion on the PR)

Fixes https://github.com/NixOS/nixos-homepage/issues/46.

This can be used to implement functions like ‘imap’ (or for that
matter, ‘map’) without the quadratic complexity incurred by calling
‘++’ repeatedly.

This is a generalisation of replaceChars in Nixpkgs.

These are used thousands of times during NixOS evaluation, so it's
useful to speed them up.

And make exportPath() less spammy by default.

This hook can be used to set system-specific per-derivation build
settings that don't fit into the derivation model and are too complex or
volatile to be hard-coded into nix. Currently, the pre-build hook can
only add chroot dirs/files through the interface, but it also has full
access to the chroot root.

The specific use case for this is systems where the operating system ABI
is more complex than just the kernel-support system calls. For example,
on OS X there is a set of system-provided frameworks that can reliably
be accessed by any program linked to them, no matter the version the
program is running on. Unfortunately, those frameworks do not
necessarily live in the same locations on each version of OS X, nor do
their dependencies, and thus nix needs to know the specific version of
OS X currently running in order to make those frameworks available. The
pre-build hook is a perfect mechanism for doing just that.

Going to reimplement differently.

This reverts commit 1e4a4a2e.

This hook can be used to set system specific per-derivation build
settings that don't fit into the derivation model and are too complex or
volatile to be hard-coded into nix. Currently, the pre-build hook can
only add chroot dirs/files.

The specific use case for this is systems where the operating system ABI
is more complex than just the kernel-supported system calls. For
example, on OS X there is a set of system-provided frameworks that can
reliably be accessed by any program linked to them, no matter the
version the program is running on. Unfortunately, those frameworks do
not necessarily live in the same locations on each version of OS X, nor
do their dependencies, and thus nix needs to know the specific version
of OS X currently running in order to make those frameworks available.
The pre-build hook is a perfect mechanism for doing just that.

If ‘build-use-chroot’ is set to ‘true’, fixed-output derivations are
now also chrooted. However, unlike normal derivations, they don't get
a private network namespace, so they can still access the
network. Also, the use of the ‘__noChroot’ derivation attribute is
no longer allowed.

Setting ‘build-use-chroot’ to ‘relaxed’ gives the old behaviour.

If ‘--option restrict-eval true’ is given, the evaluator will throw an
exception if an attempt is made to access any file outside of the Nix
search path. This is primarily intended for Hydra, where we don't want
people doing ‘builtins.readFile ~/.ssh/id_dsa’ or stuff like that.

Closes #473.

Fixes #453

Fix typo (assuming this is a typo)
`allowedRequisites` mentions `allowedReferences` in code example

‘--run’ is like ‘--command’, except that it runs the command in a
non-interactive shell. This is important if you do things like:

  $ nix-shell --command make

Hitting Ctrl-C while make is running drops you into the interactive
Nix shell, which is probably not what you want. So you can now do

  $ nix-shell --run make

instead.

'... another level of indirection not shown in the figure above ...'
but in the 'user-environments.png' figure there is '~/.nix-profile'.
the figure was updated with the commit: f982df3c on Mar 16, 2005.

  '... when when ...' -> '... when ...'