[BUG] git gui can't commit multiple files

This is a regression in git 2.11.0 (version 2.10.2 is fine).

In git-gui I select multiple files in the Unstaged Changes (using shift+click) and press ctrl+t to stage them. Then only one files gets staged instead of all of the selected files. The same happens when unstaging files.

Git-cola also exhibits the same behavior. Although there I could stage multiple files if I used a popup menu instead of the keyboard shortcut (I'm guessing it goes through a different code path?).

Note that I tested by reverting back to 2.10.2 and verified that everything works, so I'm quite certain that this is a regression in git.