pre-install script.  By default this is turned off; you should edit
  the spec file to enable it.

  set on the rpmbuild command line.

  doesn't take \Theta(n^2) space/time complexity.

  errors while running `nix-store --verify'.

  could get out of sync if multiple input derivations mapped to the
  same closure expression (since waitees is a set).

  unreachable paths that haven't been used for N hours.  For instance,
  `nix-collect-garbage --min-age 168' only deletes paths that haven't
  been accessed in the last week.

  This is useful for instance in the build farm where many derivations
  can be shared between consecutive builds, and we wouldn't want a
  garbage collect to throw them all away.  We could of course register
  them as roots, but then we'd to unregister them at some point, which
  would be a pain to manage.  The `--min-age' flag gives us a sort of
  MRU caching scheme.

  BUG: this really shouldn't be in gc.cc since that violates
  mechanism/policy separation.

  doesn't just print the set of paths that should be deleted.  So
  there is no more need to pipe the result into `nix-store --delete'
  (which doesn't even exist anymore).

  suboperations `--print-live', `--print-dead', and `--delete'.  The
  roots are not determined by nix-store; they are read from standard
  input.  This is to make it easy to customise what the roots are.

  The collector now no longer fails when store expressions are missing
  (which legally happens when using substitutes).  It never tries to
  fetch paths through substitutes.

  TODO: acquire a global lock on the store while garbage collecting.
  
* Removed `nix-store --delete'.

* Drop support for the outPath attribute in derivations.

  set the real uid and gid to the effective uid and gid, the Nix
  binaries can be installed as owned by the Nix user and group instead
  of root, so no root involvement of any kind is necessary.

  Linux and FreeBSD have these functions.

  users.

  If the configure flag `--enable-setuid' is used, the Nix programs
  nix-env, nix-store, etc. are installed with the setuid bit turned on
  so that they are executed as the user and group specified by
  `--with-nix-user=USER' and `--with-nix-group=GROUP', respectively
  (with defaults `nix' and `nix').

  The setuid programs drop all special privileges if they are executed
  by a user who is not a member of the Nix group.

  The setuid feature is a quick hack to enable sharing of a Nix
  installation between users who trust each other.  It is not
  generally secure, since any user in the Nix group can modify (by
  building an appropriate derivation) any object in the store, and for
  instance inject trojans into binaries used by other users.

  The setuid programs are owned by root, not the Nix user.  This is
  because on Unix normal users cannot change the real uid, only the
  effective uid.  Many programs don't work properly when the real uid
  differs from the effective uid.  For instance, Perl will turn on
  taint mode.  However, the setuid programs drop all root privileges
  immediately, changing all uids and gids to the Nix user and group.

* Don't use `seq' - some primitive, obsolete operating systems
  (Darwin) don't have it.

* Builder output is written to standard error by default.
  * The option `-B' is gone.
  * The option `-Q' suppresses builder output.

The result of this is that most Nix invocations shouldn't need any
flags w.r.t. logging.

* Handle multiple derivations correctly.

  "i686-linux").

  particular happens on distributed builds or when using push/pull.

  print out incorrect "build failed" messages).

  derivation disables scanning for dependencies.  Use at your own
  risk.  This is a quick hack to speed up UML image generation (image
  are very big, say 1 GB).

  It would be better if the scanner were faster, and didn't read the
  whole file into memory.

* Include bootstrap.sh in dist.

  store object just built.

  Now SuSE and Red Hat should yield the same type (`i686-linux').  Mac
  OS X should now give `powerpc-darwin' (i.e., the version number is
  gone).

  system types other than the current system.  I.e., `nix-env -i'
  won't install derivations for other system types, and `nix-env -q'
  won't show them.  The flag `--system-filter SYSTEM' can be used to
  override the system type used for filtering (but not for
  building!).  The value `*' can be used not to filter anything.

  `nix-env -q'.
* Queries can now be combined, e.g., `nix-env -q --status --system'.

  derivations with names matching the derivations being installed.
  The option `--preserve-installed / -P' overrides this behaviour.