BUG #8543: Standby recovery use incorrect timeline to determine WAL length

The following bug has been logged on the website:

Bug reference: 8543
Logged by: Alfonso Vicente
Email address: alfonso(dot)vicente(at)logos(dot)com(dot)uy
PostgreSQL version: 9.1.3
Operating system: OpenSUSE 11
Description:

Environment: PostgreSQL 9.1.3 / OpenSUSE 11

The use case is a switchover and switchback test, using a standby cluster
with Streaming Replication. We have 2 datacenters: main-site and
backup-site

The cluster in main-site has timeline ID 1, and we perform the switchover to
backup-site without any trouble. When we execute the pg_ctl promote, the
cluster sets the new timeline ID 2 (OK).

But... we don't stop the cluster in main-site. So, the cluster in main-site
continue to archive logs in /archlogs directory, and archives the WAL
00000001000000FE00000002 of 16MB.

Immediately, we perform a backup in the backup-site, to prepare for
switchback. The pg_stop_backup() force a WAL switch, and generate a WAL
00000002000000FE00000002 of 2MB. Then, the archive_command script perform
the log shipping to the main-site and store the 00000002000000FE00000002 in
the same /archlogs directory

When we execute the pg_ctl promote in the main-site, the postgresql.log show
the following error:

2013-10-19 22:39:59 UYST LOG: database system was shut down in recovery
at 2013-10-19 21:47:07 UYST
sh: /home/postgres/9.1/backups/archlogs/00000002.history.gz: No existe el
fichero o el directorio
2013-10-19 22:39:59 UYST LOG: starting archive recovery
2013-10-19 22:39:59 UYST FATAL: archive file "00000002000000FE00000002"
has wrong size: 2293760 instead of 16777216
2013-10-19 22:39:59 UYST LOG: startup process (PID 10636) exited with
exit code 1
2013-10-19 22:39:59 UYST LOG: aborting startup due to startup process
failure

The WAL 00000002000000FE00000002 is of 2293760 bytes, this is not an error.
Why PostgreSQL think WAL 00000002000000FE00000002 should be of 16MB ? ... I
think the cause can be the WAL 00000001000000FE00000002 (timeline ID 1)
stored in the /archlogs directory

If we drop all the timeline ID 1 archived WALs, the failback executes
succesfully

There is an easy workaround, but please, confirm if this is a bug. The
documentation says: "The default behavior of recovery is to recover along
the same timeline that was current when the base backup was taken". The base
backup in backup-site was timeline ID 2

Thanks in advance