This patch implements filtering out of the offline/drained nodes and
fixes a bug in IAllocator.hs parsing (similar to an older bug in Rapi.hs
from where the code was copied).

This patch implements non-mirrored instance allocation, by allocating as
secondary node “noSecondary”.

Both allocate and relocate compute new node lists, whose score must be
ranked and the best option chosen. This means we can convert the code to
a generic function.

This patch implements allocate for two node requests. One node requests
can be done as soon as we have a valid allocateOn function for single
nodes.

This patch completes the implementation of hail relocate. It maps all
valid destination nodes through a ReplaceSecondary IMove, filters out
the failed relocations, computes the resulting scores and picks the
lowest one.

This patch implements a very stupid (and broken) version of hail
‘allocate’.

This is not yet used.

Since we have Node/Instance.name, we can now simplify a few constructs.

This patch generalizes a little the CLI handling by not passing in a
special function for help and such, but instead requiring that the
options object supports some common functionality.

This new big patch does a couple of more cleanups in the loading of data
chapter:
  - introduce a Types module that holds most types (except the base
    Node/Instance/etc.) so that multiple other modules can use these
    (instead of only Cluster and its users)
  - bring IAlloc.hs in line with the recent changes of providing data
    types and not strings
  - removal of obsolete Utils.hs json-related functions

This makes hail compile and get a request parsed via IAlloc, but nothing
more.

This patch changes Cluster.loadData to return a Result, instead of
directly the values; this will allow us to return meaningful error
values (e.g. when an instances lives on unknown node) rather than simply
abort. Currently the result is always an Ok, the actual signalling of
errors will come later.

Its callers are changed to accommodate for the new return type and to
display errors as needed.

This big patch converts from our home-grown monad-like constructs
(the Either stuff) to a real, Either-like-but-another-name monad.

We introduce a “Result a” monad, and this allows dropping many of the
extra constructs. Hopefully the code is also more clear.

Many of the functions could now be written in a generic-monad style,
instead of Result specifically, but that will come in future patches.

IAlloc.hs also has some unrelated patches.

This option is the opposite of the --verbose option, and it allows
decreasing the verbosity level from the default of one to zero (which
currently doesn't show the warning messages for missing disk/memory).

This patch moves the oneline format into a separate function for easier
usage.

For clusters with no instances, there is no point in computing either
the score or in running the algorithm. In this case, we exit prematurely
and when running in one-line mode we show dummy information.

This new parameter causes the algorithm to finish (or even not start at
all) if we reach/have a score better than it.

This patch adds support for selecting the instance/node file names via
two environment variables (HTOOLS_NODES, HTOOLS_INSTANCES).

Unfortunately we still have lots of duplicated code, since the options
are not unified.

Neither hbal nor hn1 take any arguments beside the options, so if any
are passed is most likely an unintended error. This patch aborts in such
cases.

This patch adds support in hbal for writing the command list to a shell
script, with error checking and allowing for early exit.

Since it's easy to pass a wrong node name as offline, we should abort
instead of silently ignoring it.

This patch adds checking of cluster data in the binaries and display of
node's x_mem/i_mem in the node list.

This patch moves the common CLI functionality (as much as currently
possible) into a separate module. This means we only have one parseOpts
and that Utils.hs doesn't keep this kind of functions anymore.

This is added for better readability, since this is very often used in
declarations.

This patch modifies hbal (only, hn1 not yet) for setting nodes offline.

The modules are moved from the ‘top’ namespace to ‘Ganeti.HTools’, in
compliance with standard practices.

This patch moves the version string creation into a function in Utils
which shows some more information.

This patch adds a -V, --version command line option that shows the
program version and also updates the hn1 usage string (similar to hbal).

This just reorders some functions for a more logical ordering.

This patch changes the solution list to include a step counter so that
it's more clear these are successive steps (in a definite order), and
not just an unordered list of changes.

This patch added a verbose output and changed the output so that by
default it is less verbose and more clear.

This patch moves the formatting of the command list to Cluster.hs and
enhances it with separator messages between the steps.

Currently hbal does multiple rounds, stopping when a rounds doesn't
bring improvements. With the recent changes to not remove instances from
the candidate list, this is obsolete as the first round will always run
to the end of the improvements.

This patch changes this so that the Cluster.checkMove function doesn't
recurse, but just computes the next best move (as its docstring says).
This means we can actually incrementally compute and print the solution,
and this is needed as otherwise an instance could move twice and the
second time it needs the current placement to compute the exact command
line and operation needed for the move.

This patch attempts to embed the VCS id in binaries, based on the way
other projects seem to do this.

Learned how multi-line string literals work in Haskell :)

This patch automatically removes the longest common (domain, i.e.
starting with a dot) suffix from the node and instance names. This gives
a much clearer display, and this format is compatible with the way
Ganeti accepts shortened names.

Based on the node changes, we remove the N+1 check and only show a
warning instead.

Currently we always compute the available node list for moves (for an
instances) based on the nodes of the initial table. This works find,
however is a repeated calculation.

We optimize this by passing a node list (of indexes, not full objects),
which helps in two ways:
  - faster to filter later
  - allows restriction of target nodes by enforcing only this subset as
    target for moves

This patch moves a function to Utils and changes hn1 to be able to take
data from RAPI.