Commit coverage totals

Returns the coverage totals for a given commit and the
coverage totals broken down by file.

By default that commit is the head of the default branch but can also be specified explictily by:

• sha - return totals for the commit with the given SHA
• branch - return totals for the head commit of the branch with the given name

The totals can be optionally filtered by specifying:

• path - only show totals for pathnames that start with this value
• flag - only show totals that applies to the specified flag name
• component_id - only show totals that applies to the specified component