design update: symlink structure
design update: symlink structure

Update the upgrade design document according to the outcome
of the design discussion at GanetiCon 2013. There are two
changes in the design.

* As revision upgrades are binary compatible at all levels,
  one can accept a rough upgrade, just replacing the binaries.
  Therefore, it will become a configure option whether version
  includes revision and suffix, or not.

* The install/uninstall scripts are replaced in favor of another
  level of indirection. In this way, at run time, only two symlinks
  in ${sysconfdir}/ganeti, will be changed, whereas links under
  ${PREFIX}/bin, ${PREFIX}/sbin, and similar, are not touched by
  ganeti itself.

* The layout for the ganeti python libraries, which do not provide
  stable interface, are changed to be used as private modules.

Signed-off-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>
Reviewed-by: Apollon Oikonomopoulos <ed81ed0a45ccd5c8869bda52e38353a6299ee39e@gmail.com>
Reviewed-by: Michele Tartara <05f7077a2c6cbbdc4af4ba42e3ef89a0df846179@google.com>

apyrgio/snf-ganeti,yiannist/ganeti,leshchevds/ganeti,ganeti/ganeti,bitemyapp/ganeti,leshchevds/ganeti,apyrgio/snf-ganeti,mbakke/ganeti,yiannist/ganeti,mbakke/ganeti,leshchevds/ganeti,apyrgio/ganeti,ganeti/ganeti,grnet/snf-ganeti,dimara/ganeti,apyrgio/ganeti,ganeti-github-testing/ganeti-test-1,andir/ganeti,onponomarev/ganeti,onponomarev/ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,bitemyapp/ganeti,andir/ganeti,dimara/ganeti,ganeti/ganeti,grnet/snf-ganeti,andir/ganeti,mbakke/ganeti