"nix-channel --add" now accepts a second argument: the channel name.
This allows channels to have a nicer name than (say) nixpkgs_unstable.
If no name is given, it defaults to the last component of the URL
(with "-unstable" or "-stable" removed).
Also, channels are now stored in a profile
(/nix/var/nix/profiles/per-user/$USER/channels). One advantage of
this is that it allows rollbacks (e.g. if "nix-channel --update" gives
an undesirable update).
‘drvAttrs’. This will simplify the implementation of functions such
as ‘overrideDerivation’ in Nixpkgs, which need to filter out any
added attributes such as outPath.
common attribution so that they're evaluated only once, etc. Note
that the default output is now the first element of the "outputs"
attribute, rather than the first element of the sorted list of
outputs. This seems more user-friendly.
other simplifications.
* Use <nix/...> to locate the corepkgs. This allows them to be
overriden through $NIX_PATH.
* Use bash's pipefail option in the NAR builder so that we don't need
to create a temporary file.
using the build hook mechanism, by setting the derivation attribute
"preferLocalBuild" to true. This has a few use cases:
- The user environment builder. Since it just creates a bunch of
symlinks without much computation, there is no reason to do it
remotely. In fact, doing it remotely requires the entire closure
of the user environment to be copied to the remote machine, which
is extremely wasteful.
- `fetchurl'. Performing the download on a remote machine and then
copying it to the local machine involves twice as much network
traffic as performing the download locally, and doesn't save any
CPU cycles on the local machine.
Nix expressions in that directory are combined into an attribute set
{file1 = import file1; file2 = import file2; ...}, i.e. each Nix
expression is an attribute with the file name as the attribute
name. Also recurses into directories.
* nix-env: removed the "--import" (-I) option which set the
~/.nix-defexpr symlink.
* nix-channel: don't use "nix-env --import", instead symlink
~/.nix-defexpr/channels. So finally nix-channel --update doesn't
override any default Nix expressions but combines with them.
This means that you can have (say) a local Nixpkgs SVN tree and use
it as a default for nix-env:
$ ln -s .../path-to-nixpkgs-tree ~/.nix-defexpr/nixpkgs_svn
and be subscribed to channels (including Nixpkgs) at the same time.
(If there is any ambiguity, the -A flag can be used to
disambiguate, e.g. "nix-env -i -A nixpkgs_svn.pan".)
;-)
* Channels: fix channels that are plain lists of derivations (like
strategoxt-unstable) instead of functions (like nixpkgs-unstable).
This fixes the error message "error: the left-hand side of the
function call is neither a function nor a primop (built-in
operation) but a list".
get the basename of the channel URL (e.g., nixpkgs-unstable). The
top-level Nix expression of the channel is now an attribute set, the
attributes of which are the individual channels (e.g.,
{nixpkgs_unstable = ...; strategoxt_unstable = ...}). This makes
attribute paths ("nix-env -qaA" and "nix-env -iA") more sensible,
e.g., "nix-env -iA nixpkgs_unstable.subversion".
user environment collission between two packages due to overlapping
file names, then a package with a higher priority will overwrite the
symlinks of a package with a lower priority. E.g.,
$ nix-env --set-flag priority 5 gcc
$ nix-env --set-flag priority 10 binutils
gives gcc a higher priority than binutils (higher number = lower
priority).
allow switching between them (NIX-80).
Example: two versions of Pan:
$ nix-env -q pan
pan-0.128
pan-0.14.2.91
$ readlink $(which pan)
/nix/store/l38jrbilw269drpjkx7kinhrxj6fjh59-pan-0.14.2.91/bin/pan
At most one of them can be active any given time. Assuming than
0.14.2.91 is active, you can active 0.128 as follows:
$ nix-env --set-flag active false pan-0.14.2.91
$ nix-env --set-flag active true pan-0.128
$ readlink $(which pan)
/nix/store/nziqwnlzy7xl385kglxhg75pfl5i936n-pan-0.128/bin/pan
More flags to follow.
derivations. This is mostly to simplify the implementation of
nix-prefetch-{url, svn}, which now work properly in setuid
installations.
* Enforce valid store names in `nix-store --add / --add-fixed'.
* Formalise the notion of fixed-output derivations, i.e., derivations
for which a cryptographic hash of the output is known in advance.
Changes to such derivations should not propagate upwards through the
dependency graph. Previously this was done by specifying the hash
component of the output path through the `id' attribute, but this is
insecure since you can lie about it (i.e., you can specify any hash
and then produce a completely different output). Now the
responsibility for checking the output is moved from the builder to
Nix itself.
A fixed-output derivation can be created by specifying the
`outputHash' and `outputHashAlgo' attributes, the latter taking
values `md5', `sha1', and `sha256', and the former specifying the
actual hash in hexadecimal or in base-32 (auto-detected by looking
at the length of the attribute value). MD5 is included for
compatibility but should be considered deprecated.
* Removed the `drvPath' pseudo-attribute in derivation results. It's
no longer necessary.
* Cleaned up the support for multiple output paths in derivation store
expressions. Each output now has a unique identifier (e.g., `out',
`devel', `docs'). Previously there was no way to tell output paths
apart at the store expression level.
* `nix-hash' now has a flag `--base32' to specify that the hash should
be printed in base-32 notation.
* `fetchurl' accepts parameters `sha256' and `sha1' in addition to
`md5'.
* `nix-prefetch-url' now prints out a SHA-1 hash in base-32. (TODO: a
flag to specify the hash.)
