Share all of Onedrive with another user

- Open the user's OneDrive Documents (root, top level) and click the gear next to the profile in the upper right
- select Site Settings
- select Site Permissions
there will be a yellow alert box stating that content on the site exists with different permissions assigned
- click the "Show these items" hyperlink
a dialog pops up
- select the "manage permissions" hyperlink next to Documents
- click the Grant Permissions button in the ribbon
- you are then presented with the standard OneDrive/SharePoint share dialog box for the root, top level, parent of all folders and files in the user's OneDrive.