* Preliminary NEWS for 0.8.

NEWS

@@ -1,3 +1,145 @@
+Version 0.8
+
+NOTE: the hashing scheme in Nix 0.8 changed (as detailed below).  As a
+result, `nix-pull' manifests and channels built for Nix 0.7 and below
+will now work anymore.  However, the Nix expression language has not
+changed, so you can still build from source.  Also, existing user
+environments continue to work.  Nix 0.8 will automatically upgrade the
+database schema of previous installations when it is first run.
+
+* The cryptographic hashes used in store paths are now 160 bits long,
+  but encoded in base-32 so that they are still only 32 characters
+  long (e.g., /nix/store/csw87wag8bqlqk7ipllbwypb14xainap-atk-1.9.0).
+  (This is actually a 160 bit truncation of a SHA-256 hash.)
+
+* Big cleanups and simplifications of the basic store semantics.  The
+  notion of "closure store expressions" is gone (and so is the notion
+  of "successors"); the file system references of a store path are now
+  just stored in the database.
+
+  For instance, given any store path, you can query its closure:
+
+    $ nix-store -qR $(which firefox)
+    ... lots of paths ...
+
+  Also, Nix now remembers for each store path the derivation that
+  built it (the "deriver"):
+
+    $ nix-store -qR $(which firefox)
+    /nix/store/4b0jx7vq80l9aqcnkszxhymsf1ffa5jd-firefox-1.0.1.drv
+
+  So to see the build-time dependencies, you can do
+  
+    $ nix-store -qR $(nix-store -qd $(which firefox))
+
+  or, in a nicer format:
+
+    $ nix-store -q --tree $(nix-store -qd $(which firefox))
+
+  File system references are also stored in reverse.  For instance,
+  you can query all paths that directly or indirectly use a certain
+  Glibc:
+
+    $ nix-store -q --referers-closure \
+        /nix/store/8lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4
+
+* The concept of fixed-output derivations has been formalised.
+  Previously, functions such as `fetchurl' in Nixpkgs used a hack
+  (namely, explicitly specifying a store path hash) to prevent changes
+  to, say, the URL of the file from propagating upwards through the
+  dependency graph, causing rebuilds of everything.  This can now be
+  done cleanly by specifying the `outputHash' and `outputHashAlgo'
+  attributes.  Nix itself checks that the content of the output has
+  the specified hash.  (This is important for maintaining certain
+  invariants necessary for future work on secure shared stores.)
+
+* One-click installation :-)  It is now possible to install any
+  top-level component in Nixpkgs directly, through the web - see,
+  e.g., http://catamaran.labs.cs.uu.nl/dist/nixpkgs-0.8/.  All you
+  have to do is associate `/nix/bin/nix-install-package' with
+  `application/nix-package' (or the extension `.nixpkg'), and clicking
+  on a package link will cause it to be installed, with all
+  appropriate dependencies.  If you just want to install some specific
+  application, this is easier than subscribing to a channel.
+
+* `nix-store -r PATHS' now builds all the derivations PATHS in
+  parallel.  Previously it did them sequentially (though exploiting
+  possible parallelism between subderivations).  This is nice for
+  build farms.
+
+* `nix-channel' has new operations `--list' and `--remove'.
+
+* New ways of installing components into user environments:
+
+  - Copy from another user environment:
+
+      $ nix-env -i --from-profile .../other-profile firefox
+
+  - Install a store derivation directly (bypassing the Nix expression
+    language entirely):
+
+      $ nix-env -i /nix/store/z58v41v21xd3...-aterm-2.3.1.drv
+
+    (This is used to implement `nix-install-package', which is
+    therefore immune to evolution in the Nix expression language.)
+
+  - Install an already built store path directly:
+
+      $ nix-env -i /nix/store/hsyj5pbn0d9i...-aterm-2.3.1
+
+  - Install the result of a Nix expression specified as a command-line
+    argument:
+
+      $ nix-env -f .../i686-linux.nix -i -E 'x: x.firefoxWrapper'
+
+    The difference with the normal installation mode is that `-E' does
+    not use the `name' attributes of derivations.  Therefore, this can
+    be used to disambiguate multiple derivations with the same name.
+
+* A hash of the contents of a store path is now stored in the database
+  after a succesful build.  This allows you to check whether store
+  paths have been tampered with: `nix-store --verify --check-contents'.
+    
+* Implemented a concurrent garbage collector.  It is now always safe
+  to run the garbage collector, even if other Nix operations are
+  happening simultaneously.
+
+  However, there can still be GC races if you use `nix-instantiate'
+  and `nix-store -r' directly to build things.  To prevent races, use
+  the `--add-root' flag of those commands.
+
+* The garbage collector now finally deletes paths in the right order
+  (i.e., topologically sorted under the `references' relation), thus
+  making it safe to interrupt the collector without risking a store
+  that violates the closure invariant.
+
+* Likewise, the substitute mechanism now downloads files in the right
+  order, thus preserving the closure invariant at all times.
+
+* The result of `nix-build' is now registered as a root of the garbage
+  collector.  If the `./result' link is deleted, the GC root
+  disappears automatically.
+
+* The behaviour of the garbage collector can be changed globally by
+  setting options in `/nix/etc/nix/nix.conf'.
+
+  - `gc-keep-derivations' specifies whether deriver links should be
+    followed when searching for live paths.
+
+  - `gc-keep-outputs' specifies whether outputs of derivations should
+    be followed when searching for live paths.
+  
+  - `env-keep-derivations' specifies whether user environments should
+    store the paths of derivations when they are added (thus keeping
+    the derivations alive).
+
+* New `nix-env' query flags `--drv-path' and `--out-path'.
+
+* `fetchurl' allows SHA-1 and SHA-256 in addition to MD5.  Just use
+  `sha1 = ' or `sha256 = ' instead of `md5 = '.  Of course, they're
+  all unsafe, really ;-)
+
+  
 Version 0.7
 
 * Binary patching.  When upgrading components using pre-built binaries