This patch changes the backend selection method in CLI to prefer, in order:
  - a RAPI specification
  - a Luxi specification
  - and finally the node/instance files

It also modifies hspace and hbal to provide a ‘-L’ command line option
for enabling Luxi.

Currently hspace doesn't handle failures from tryAlloc correctly; this
patch changes the iterateDepth function in hspace to return a Result (…)
so that errors can be propagated correctly.

The patch also changes one output key to be more clear and a typo in
Cluster.hs

Currently, the tryAlloc and tryReloc function return a list with all the
results, both failures and successes. This is fine for hail, which does
one round of allocations, but is not so good for hspace, which does
iterative rounds; since at each (successful) step we only take the best
solution, it means that we're using lots of heap space to compute and
store node lists which are thrown away at the end of the step.

This patch changes these two functions and their callers in hail/hspace
to only return the best solution, and error/success counters. This
allows hspace to run in a much smaller space, and reduces GC cost
greatly.

Overall, it is a cleanup, as hail/hspace did a lot of work to chose this
best solution, whereas now it's automatically promoted within
Cluster.concatAllocs.

Currently the Cluster.AllocSolution type is defined as a list of
‘(OpResult Node.list, …)’ and the results for applyMove are defined as
‘(OpResult Node.List, …)’. Both these means that the failure/success
indication is hidden in the first elements of this tuple, which makes is
harder to add other elements depending on the success/failure (like the
score for the new node list).

This patch moves the OpResult to outside of the tuple, in effect making
all these ‘OpResult (…)’ which makes the internal tuple elements
consistent. The patch is affecting the applyMove, tryAlloc and
tryRealloc functions, and only briefly the hail and hspace programs.

This (big) patch changes the output of hspace from text-format
(separated by ‘: ’) to a shell-snippet, in ‘key=value’ format.

This will allow sourcing the output or parsing it via awk/sed/etc.

Currently the instance count and cluster score are separated from the
other initial/final phase stats, even though they are very similar. This
patch moves computation of these two into totalResources/CStats and
removes special printing in hspace.

This patch changes Cluster.totalResources to compute more resources and
prints them in hspace.

Currently many of the exit and warning conditions mistakenly display error
messages on stdout, which makes parsing the output of programs harder. This
patch attempts to fix such occurrences.

Currently hspace exits with an error if the cluster is not N+1 compliant
at the beginning of the run. This patch changes hspace such that this
condition is instead treated as a zero-allocation-possible, FailN1 mode.
This allows the same stats to be reported in this case as in the normal
case.

This is mostly for user-friendliness in the default mode, when we don't
specify the instance parameters.

This big patch cleans up the code per hlint indications. Many removals
of extra parentheses, replacements of concat . map with concabtMap,
extra dollar signs, eta reductions, etc. were performed.

The code still compiles and passes a couple of manual tests on sample
files. The individual changes are also small enough as to be visually
easy to confirm.

This patch enhances hspace to report why the allocation sequence
stopped, both in absolute error count and for the top reason.

Currently the allocation/move operations workflow return ‘Maybe a’,
which is very convenient but loses all details about the failure mode.

This patch introduces a new data type which encodes the specific failure
mode. It is not yet used correctly (e.g. all node operations result in
FailN1), but the workflow is updated. Most of the changes are in the
hail/hspace tools, the library code required only trivial adjustments.

This adds two new stats - sum of reserved ram and disk.

This uses the newly-added Node.availDisk to compute the actual available
disk correctl, and display the total allocatable disk in hspace.

Currently totalResources returns a 5-tuple of integers. This is not easy
to handle, as each change on the return type means that each caller must
be updated.

This patch adds a new type for cluster stats and uses that instead as
its return type. This simplifies its callers while complicating only a
little the computation of the stats.

The display of cluster resources is extracted into a separate function
and enhanced to display more stats.

This patch changes Cluster.totalResources to compute more details about
the cluster status, and enhances hspace to display more of these.

This removes some unused functions and imports to cleanup the warnings.

In a few places (e.g. tryRead or any printf call) it's a little bit hard
to add the correct type signatures, but in the it is possible to fix
these warnings (which can bite one in subtle cases).

This patch adds reading of vcpu count for instances, in preparation for
using the vcpu ratio in cluster scoring.

This also fixes other required node numbers.

Currently tryAlloc/tryReloc do not return the new instance, as this is
not needed for IAllocator alloc/reloc requests. However, for computing
the space, the new instance is useful, so we modify these functions to
return this information too.

The patch also improves hspace to have (with default parameters) a
parseable output.

This is a tool that checks how many instances (of same size, specified
by command line arguments) can be added to a cluster while remaining N+1
compliant.