gitk: Fallback to selecting the head commit upon load

Try selecting the head, if the previously selected commit
is not available in the new view.

Signed-off-by: Alexander Gavrilov <angavrilov@gmail.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

gitk

@@ -1506,9 +1506,16 @@ proc chewcommits {} {
 	global numcommits startmsecs
 
 	if {[info exists pending_select]} {
+	    update
+	    reset_pending_select {}
+
+	    if {[commitinview $pending_select $curview]} {
+		selectline [rowofcommit $pending_select] 1
+	    } else {
 		set row [first_real_row]
 		selectline $row 1
 	    }
+	}
 	if {$commitidx($curview) > 0} {
 	    #set ms [expr {[clock clicks -milliseconds] - $startmsecs}]
 	    #puts "overall $ms ms for $numcommits commits"
@@ -3372,16 +3379,20 @@ proc showview {n} {
     drawvisible
     if {$row ne {}} {
 	selectline $row 0
-    } elseif {$mainheadid ne {} && [commitinview $mainheadid $curview]} {
-	selectline [rowofcommit $mainheadid] 1
     } elseif {!$viewcomplete($n)} {
 	reset_pending_select $selid
+    } else {
+	reset_pending_select {}
+
+	if {[commitinview $pending_select $curview]} {
+	    selectline [rowofcommit $pending_select] 1
 	} else {
 	    set row [first_real_row]
 	    if {$row < $numcommits} {
 		selectline $row 0
 	    }
 	}
+    }
     if {!$viewcomplete($n)} {
 	if {$numcommits == 0} {
 	    show_status [mc "Reading commits..."]