Rather than just counting builds where the derivation matches, select builds
based on the derivation outputs, which accounts for different but equivalent
derivations.
Derivations are effectively equivalent if they produce the same set of
outputs, which is possible because of the equivalence of fixed output
derivations. A fixed output derivation can be different, but equivalent,
because it produces the same fixed output.
To better allow tracking equivalent derivations, primarily to allow working
out what derivations might correspond to a build, store the sets of derivation
outputs, and which derivations they relate to.
The join on derivation_outputs was completely wrong, so fix that.
Also, rather than only selecting outputs where there's a corresponding build,
just eliminate outputs where there is an entry in the nars table, fetched from
the relevant build server.
Also just look at x86_64-linux derivations, because there's no filtering on
relevant derivations for a build server at the moment.
Rather than eliminating any derivation that has a known build, eliminate those
derivations, but also equivalent derivations as well.
For selecting the derivations in a revision, join on the equivalent
derivations, as all the equilalent derivations need checking as well, as it's
unknown which one Cuirass would have associated the build against.
Also, filter for x86_64-linux, to avoid checking for crossbuilt things. This
should be replaced by some way of describing what derivations a build server
has.
Duplicate builds could creep in if the code to create them ran concurrently. I
didn't exclude them initially, as I was unsure if there should be such a
restriction, but at least for now, Cuirass builds map exactly to a single
derivation, so use the same restriction here.
Cuirass provides a timestamp field in build responses, and sometimes this
means when the build was scheduled, but when the build is finished, it's the
stoptime.
So only use the timestamp when the build hasn't finished.
Previously, all the entries for the branch were deleted, but not, only the
entries for the branch, that are present in the revision that was loaded will
be deleted. This is more efficient, as it avoids deleting and recreating
entries in the table that shouldn't have changed.
Allow for build status information to be submitted by POST request. This
required some changes to the builds and build_status tables, as for example,
the Cuirass build id may not be available, and the derivation may not be know
yet, so just record the derivation file name.
The intent with these tokens is for them to be provided when build events are
submitted, preventing unauthorised submission of build events.
It should be possible to make the database public, so it shouldn't contain any
secret information. To have secret tokens that aren't in the database, store a
token seed, and combine this with some secret data to compute the secret.
