Add support for Google's Repo tool

Problem Definition

Google has introduced a tool called Repo, which is built on top of git and allows multiple repositories to be wrapped into one location and treated as a single unit. Customers would like to make use of this to allow build plans to be linked to a Google Repo repository (a wrapped set of repositories), and therefore allow the existing functionality of change detection and branch detection to be triggered by any one of the repositories contained within a Google Repo wrapper

Suggested Solution

Add Google Repo as a new linked repository type, to allow for all existing functionality around change detection and branch detection to be used by a Google Repo wrapped set of repositories

Workaround

Customers would have to either specify a set of repositories manually within each build plan or define a custom Repo command to perform their checkouts - neither of these would allow users to take advantage of Bamboo's change & branch detection features