Upgrade from postgresql-9.5alpha1 to postgresql-9.5alpha2 (Debian packages)

It looks like the catalog version has changed between 9.5alpha1 and
9.5alpha2:

 FATAL:  database files are incompatible with server
 DETAIL:  The database cluster was initialized with CATALOG_VERSION_NO 201506282,
          but the server was compiled with CATALOG_VERSION_NO 201507281.
 HINT:  It looks like you need to initdb.

Normally, one would use pg_upgradecluster to do the upgrade, but
pg_upgradecluster assumes that the old and new version are installed in
parallel. Likewise, the low-level tool pg_upgrade needs the old bindir,
if I read the man-page correctly, and of course, apt-get upgrade
overwrites that, since it's just two versions of the same package
(unlike a major upgrade which is a new package).

So, what's the best way to do the upgrade?

* Copy the bindir before the upgrade (or restore from backup) to a safe
  place and do pg_upgrade?
* Initdb a new cluster and restore yesterdays backup?
* Something else?

    hp

--
   _  | Peter J. Holzer    | I want to forget all about both belts and
|_|_) |                    | suspenders; instead, I want to buy pants
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