mono/monodevelop — pull request #268 by Therzok (2013-04-29 13:57:11+00:00)
Title: Added left/right key navigation in solution viewer.

lluis suggested I should base it on cases. As in, only allow left/right key navigation where only one node is selected.

Left key on file navigates you to parent folder. Left key on folder while collapsed, navigates to its parent folder/project.
Right key on folder navigates to its first child if expanded.