Explain online reindexing in 2.11 release

Running the reindex program on large site can take a vary long time,
which is bad because during this time the system is down. Fortunately
Gerrit supports online reindexing if a secondary index with an older
version already exists. Explain in the release notes under which
conditions online reindexing is possible. Online reindexing in 2.11
requires an index version of 10, since older index versions have been
deleted [1].

[1] https://gerrit-review.googlesource.com/62684

Change-Id: I9a4ee7151057a30a3ea732ecc2f4affb6c06c1b1
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
1 file changed