Install tk8.5, if not yet installed:
# apt-get install tk8.5
# update-alternatives --config wish
Selection Alternative
-----------------------------------------------
1 /usr/bin/wish8.4
*+ 2 /usr/bin/wish-default
3 /usr/bin/wish8.5</pre>
There are 3 alternatives which provide wish.
Type in the number that corresponds to tk8.5 (in my case was 3) then hit enter.
Change fonts in ~/.gitk to DejaVu Sans Mono.
set mainfont {{DejaVu Sans Mono} 9}
set textfont {{DejaVu Sans Mono} 9}
set uifont {{DejaVu Sans Mono} 9 bold}