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  builder and generate a Jetty configuration file with XSLT.

  argument.

  suffix, e.g., `builtins.toFile "builder.sh" "..."'.
* toFile: handle references to other files correctly.

  easier; no longer need a helper expression).

* Documented nix-{pack,unpack}-closure.

  for packages that should be propagated to the user environment.

  *after* the packages that have been explicitly installed, and
  collisions are ignored.

  (e.g., "java-front-0.9pre15899" instead of "java-front";
  particularly important when doing upgrades later on).

  a different location than the user's.  This makes channels usable as
  a source deployment mechanism for people who install Nix under
  non-standard prefixes.  (NIX-57)

  side should be a path, I guess.
* Handle paths that are in the store but not direct children of the
  store directory.
* Ugh, hack to prevent double context wrapping.

* Primop `pathExists' to check for path existence.

* Put common test functions in tests/lang/lib.nix.

  With this primitive, a list-flattening function can be implemented
  (NIX-55, example is in tests/lang/eval-okay-flatten.nix).