git-gui: right half window is paned

For long descriptions it would be nice to be able to resize
the comment text field.

Signed-off-by: Max Kirillov <max@max630.net>
Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>

git-gui.sh

@@ -3210,13 +3210,19 @@ unset i
 
 # -- Diff and Commit Area
 #
-${NS}::frame .vpane.lower -height 300 -width 400
+${NS}::panedwindow .vpane.lower -orient vertical
 ${NS}::frame .vpane.lower.commarea
-${NS}::frame .vpane.lower.diff -relief sunken -borderwidth 1
-pack .vpane.lower.diff -fill both -expand 1
-pack .vpane.lower.commarea -side bottom -fill x
+${NS}::frame .vpane.lower.diff -relief sunken -borderwidth 1 -height 500
+.vpane.lower add .vpane.lower.diff
+.vpane.lower add .vpane.lower.commarea
 .vpane add .vpane.lower
-if {!$use_ttk} {.vpane paneconfigure .vpane.lower -sticky nsew}
+if {$use_ttk} {
+	.vpane.lower pane .vpane.lower.diff -weight 1
+	.vpane.lower pane .vpane.lower.commarea -weight 0
+} else {
+	.vpane.lower paneconfigure .vpane.lower.diff -stretch always
+	.vpane.lower paneconfigure .vpane.lower.commarea -stretch never
+}
 
 # -- Commit Area Buttons
 #