git-gui: Reverted file name text field to a label.

So although a text field with a flat relief looks like a label on
Windows it doesn't on Mac OS X.  The Aqua version of Tk is still
drawing a border around the text field and that makes the diff pane
header look pretty ugly.

Earlier I had made the file name area into a text widget so the user
could highlight parts of it and copy them onto the clipboard; but with
the context menu being present this isn't quite as necessary as the user
can copy the file name to the clipboard using that instead.  So although
this is a small loss in functionality for non-Mac OS X systems I think it
is still reasonable.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

git-gui

@@ -2290,33 +2290,23 @@ label .vpane.lower.diff.header.l1 -text {File:} \
 	-background orange \
 	-font font_ui
 set ui_fname .vpane.lower.diff.header.l2
-text $ui_fname \
+label $ui_fname \
+	-textvariable ui_fname_value \
 	-background orange \
-	-height 1 \
-	-wrap none \
-	-relief flat \
-	-state disabled \
+	-anchor w \
+	-justify left \
 	-font font_ui
 menu $ui_fname.ctxm -tearoff 0
-$ui_fname.ctxm add command -label "Copy Only Selection" \
+$ui_fname.ctxm add command -label "Copy" \
 	-font font_ui \
-	-command "tk_textCopy $ui_fname"
-$ui_fname.ctxm add command -label "Copy Complete Name" \
-	-font font_ui \
-	-command "
-		$ui_fname tag add sel 0.0 {end -1c}
-		tk_textCopy $ui_fname
-		$ui_fname tag remove sel 0.0 end
-	"
+	-command {
+		clipboard clear
+		clipboard append \
+			-format STRING \
+			-type STRING \
+			-- $ui_fname_value
+	}
 bind_button3 $ui_fname "tk_popup $ui_fname.ctxm %X %Y"
-trace add variable ui_fname_value write $ui_fname.update
-proc $ui_fname.update {varname args} {
-	global ui_fname ui_fname_value
-	$ui_fname configure -state normal
-	$ui_fname delete 0.0 end
-	$ui_fname insert end [escape_path $ui_fname_value]
-	$ui_fname configure -state disabled
-}
 pack .vpane.lower.diff.header.l4 -side left
 pack .vpane.lower.diff.header.l1 -side left
 pack $ui_fname -fill x