Merge branch 'er/ui'

* er/ui:
  Always bind the return key to the default button
  Do not break git-gui messages into multiple lines.
  Improve look-and-feel of the git-gui tool.
  Teach git-gui to use the user-defined UI font everywhere.
  Allow wish interpreter to be defined with TCLTK_PATH

diff --cc git-gui.sh
Simple merge