Add support and CLI option to search multiple refs for last import

When auto-detecting the most recent point in the history of the current
branch to be updated that came from upstream, need to support searching
more than the given upstream reference where the user is switching the
upstream branch being tracked.

Use a default of 'upstream/*' and add a CLI option to set a different
pattern to be searched in cases where the repository is not using the
same naming.

The CLI option '--search-refs' may be specified multiple times to
provide multiple ref patterns to be searched using simple globbing. The
default if none provided by the user is 'upstream/*'.

Change-Id: If890d1bee015d6b495a5caa60dd8f7783cf7c4e0
Closes-Bug: #1380652