git-gui: Support applying a range of changes at once

Multiple lines can be selected in the diff viewer and applied all
at once, rather than selecting "Stage Line For Commit" on each
individual line.

Signed-off-by: Jeff Epler <jepler@unpythonic.net>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
2 files changed