Merge branch 'ml/tcl86'

* ml/tcl86:
  git-gui: remove non-ttk code
  git-gui: remove ${NS} indirection for ttk
  git-gui: always use themed widgets from ttk
  git-gui: remove redundant check for Tk >= 8.5
  git-gui: remove unreachable Tk 8.4 code
  git-gui: Make TclTk 8.6 the minimum, allow 8.7

Signed-off-by: Johannes Sixt <redacted>

diff --cc git-gui.sh
Simple merge

diff --cc lib/blame.tcl
Simple merge

diff --cc lib/choose_repository.tcl
Simple merge

diff --cc lib/remote_branch_delete.tcl
Simple merge