gitk: Highlight first search result immediately on incremental search

When typing in the "Search" field, select the current search result (so
that it gets highlighted in orange). This makes it easier to understand
what will happen if you then type Ctrl-S.

Signed-off-by: Stefan Haller <stefan@haller-berlin.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>

gitk

@@ -8053,9 +8053,12 @@ proc incrsearch {name ix op} {
 	}
     }
     if {$searchstring ne {}} {
-	set here [$ctext search $searchdirn -- $searchstring anchor]
+	set here [$ctext search -count mlen $searchdirn -- $searchstring anchor]
 	if {$here ne {}} {
 	    $ctext see $here
+	    set mend "$here + $mlen c"
+	    $ctext tag remove sel 1.0 end
+	    $ctext tag add sel $here $mend
 	    suppress_highlighting_file_for_current_scrollpos
 	    highlightfile_for_scrollpos $here
 	}