XZ compresses significantly better than bzip2. Here are the
compression ratios and execution times (using 4 cores in parallel) on
my /var/run/current-system (3.1 GiB):
bzip2: total compressed size 849.56 MiB, 30.8% [2m08]
xz -6: total compressed size 641.84 MiB, 23.4% [6m53]
xz -7: total compressed size 621.82 MiB, 22.6% [7m19]
xz -8: total compressed size 599.33 MiB, 21.8% [7m18]
xz -9: total compressed size 588.18 MiB, 21.4% [7m40]
Note that compression takes much longer. More importantly, however,
decompression is much faster:
bzip2: 1m47.274s
xz -6: 0m55.446s
xz -7: 0m54.119s
xz -8: 0m52.388s
xz -9: 0m51.842s
The only downside to using -9 is that decompression takes a fair
amount (~65 MB) of memory.
Ensuring that the tests work from the build tree requires a growing
number of nasty hacks. The tests also don't verify that the installed
Nix actually works. Thus, the tests now require "make install" to
have been run.
Nix now requires SQLite and bzip2 to be pre-installed. SQLite is
detected using pkg-config. We required DBD::SQLite anyway, so
depending on SQLite is not a big problem.
The --with-bzip2, --with-openssl and --with-sqlite flags are gone.
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".
externals directory. This is in particular useful because though
most systems have bzip2/bunzip2, they don't always have libbz2,
which we need for bsdiff/bspatch.
