git-gui: use themed tk widgets with Tk 8.5

This patch enables the use of themed Tk widgets with Tk 8.5 and above.
These make a significant difference on Windows in making the
application appear native. On Windows and MacOSX ttk defaults to the
native look as much as possible. On X11 the user may select a theme
using the TkTheme XRDB resource class by adding an line to the
.Xresources file. The set of installed theme names is available using
the Tk command 'ttk::themes'. The default on X11 is similar to the current
un-themed style - a kind of thin bordered motif look.

A new git config variable 'gui.usettk' may be set to disable this if
the user prefers the classic Tk look. Using Tk 8.4 will also avoid the
use of themed widgets as these are only available since 8.5.

Some support is included for Tk 8.6 features (themed spinbox and native
font chooser for MacOSX and Windows).

Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

lib/branch_delete.tcl

@@ -9,41 +9,40 @@ field w_check         ; # revision picker for merge test
 field w_delete        ; # delete button
 
 constructor dialog {} {
-	global current_branch
+	global current_branch use_ttk NS
 
-	make_toplevel top w
+	make_dialog top w
+	wm withdraw $w
 	wm title $top [append "[appname] ([reponame]): " [mc "Delete Branch"]]
 	if {$top ne {.}} {
 		wm geometry $top "+[winfo rootx .]+[winfo rooty .]"
 	}
 
-	label $w.header -text [mc "Delete Local Branch"] -font font_uibold
+	${NS}::label $w.header -text [mc "Delete Local Branch"] \
+		-font font_uibold -anchor center
 	pack $w.header -side top -fill x
 
-	frame $w.buttons
+	${NS}::frame $w.buttons
 	set w_delete $w.buttons.delete
-	button $w_delete \
+	${NS}::button $w_delete \
 		-text [mc Delete] \
 		-default active \
 		-state disabled \
 		-command [cb _delete]
 	pack $w_delete -side right
-	button $w.buttons.cancel \
+	${NS}::button $w.buttons.cancel \
 		-text [mc Cancel] \
 		-command [list destroy $w]
 	pack $w.buttons.cancel -side right -padx 5
 	pack $w.buttons -side bottom -fill x -pady 10 -padx 10
 
-	labelframe $w.list -text [mc "Local Branches"]
+	${NS}::labelframe $w.list -text [mc "Local Branches"]
 	set w_heads $w.list.l
-	listbox $w_heads \
+	slistbox $w_heads \
 		-height 10 \
 		-width 70 \
 		-selectmode extended \
-		-exportselection false \
-		-yscrollcommand [list $w.list.sby set]
-	scrollbar $w.list.sby -command [list $w.list.l yview]
-	pack $w.list.sby -side right -fill y
+		-exportselection false
 	pack $w.list.l -side left -fill both -expand 1
 	pack $w.list -fill both -expand 1 -pady 5 -padx 5
 
@@ -67,6 +66,7 @@ constructor dialog {} {
 	"
 	bind $w <Key-Escape> [list destroy $w]
 	bind $w <Key-Return> [cb _delete]\;break
+	wm deiconify $w
 	tkwait window $w
 }