It's pointless to store these, since Nix knows where the logs are.
Also handle (in fact require) Nix's new log storage scheme. Also some
cleanups in the build page.
The check to see whether a build had been scheduled in a previous
evaluation took about 200 ms for the nixpkgs:trunk jobset. Given
that it has more than 15000 builds, this added up to a lot. Now
it takes 0.2 ms per build.
This happened in a pathological case in Nixpkgs: the "grub" job is
evaluated for i686-linux and x86_64-linux, but in the latter case it
returns the same derivation as in the former case. So only one build
should be added.
This gets rid of the openHydraDB function and ensures that we
open the database in a consistent way.
Also drop the PostgreSQL sequence hacks. They don't seem to be
necessary anymore.
When checking whether the jobset is unchanged, we need to compare with
the previous JobsetEval regardless of whether it had new builds.
Otherwise we'll keep adding new JobsetEval rows.
* Don't use isCurrent anymore; instead look up builds in the previous
jobset evaluation. (The isCurrent field is still maintained because
it's still used in some other places.)
* To determine whether to perform an evaluation, compare the hash of
the current inputs with the inputs of the previous jobset
evaluation, rather than checking if there was ever an evaluation
with those inputs. This way, if the inputs of an evaluation change
back to a previous state, we get a new jobset evaluation in the
database (and thus the latest jobset evaluation correctly represents
the latest state of the jobset).
* Improve performance by removing some unnecessary operations and
adding an index.
The abbreviated Git revision hash (e.g. "267480b") is typically
contained in ‘gitTag’ as well, but the latter can contain other
elements as well, e.g., the delta to the closest tag. That may
be undesirable in version strings, so this is an alternative.
The ‘revCount’ attribute is the number of commits in the history
of the revision. This is useful if you need a monotonically
increasing version number.
The ‘gitTag’ attribute is the output of ‘git describe’, e.g.
‘v1.0.4-14-g2414721’ to indicate that the current revision is 14
commits after the tag ‘v1.0.4’.
In hydra-evaluator, reuse an SVN working copy between runs (similar to
what we do with Git and other input types). This reduces network
traffic in the common case.
Also, don't use nix-prefetch-svn. It doesn't do anything useful.
