git: git gui does not start anymore

[pmenzel]

Peter reported an issue:

BUG! git gui not working

see also https://www.spinics.net/lists/git/msg300157.html

Go into a git repository, and execute git gui.

~/bee-files> git gui
Error in startup script: wrong # args: should be "ttk::style theme use theme"
    while executing
"ttk::style theme use"
    (procedure "ttext" line 4)
    invoked from within
"ttext $ui_workdir -background white -foreground black \
	-borderwidth 0 \
	-width 20 -height 10 \
	-wrap none \
	-takefocus 1 -highlightthickness 1\
	..."
    (file "/usr/libexec/git-core/git-gui" line 3190)