gitk: Fix another collection of bugs

* Fixed a bug that occasionally resulted in Tcl "can't use empty string
  as argument to incr" errors - rowofcommit was sometimes not calling
  update_arcrows when it needed to.

* Fixed a "no such element in array" error when removing a fake row,
  by unsetting currentid and selectedline in removerow if the row we
  are removing is the currently selected row.

* Made the "update commits" function always do "reread references".

* Made dodiffindex et al. remove the fake row(s) if necessary.

* Fixed a bug where clicking on a row in the graph display pane didn't
  account for horizontal scrolling of the pane.

* Started changing things that cached information based on row numbers
  to use commit IDs instead -- this converts the "select line" items
  that are put into the history list to use "select by ID" instead.

* Simplified redrawtags a bit, and fixed a bug where it would use the
  mainfont for working out how far it extends to the right in the graph
  display pane rather than the actual font (which might be bold).

* Fixed a bug where "reread references" wouldn't notice if the currently
  checked-out head had changed.

Signed-off-by: Paul Mackerras <paulus@samba.org>

gitk

@@ -174,6 +174,7 @@ proc updatecommits {} {
     if {$showlocalchanges && [commitinview $mainheadid $curview]} {
 	dodiffindex
     }
+    rereadrefs
     set view $curview
     set commits [exec git rev-parse --default HEAD --revs-only \
 		     $viewargs($view)]
@@ -218,8 +219,6 @@ proc updatecommits {} {
     incr viewactive($view)
     set viewcomplete($view) 0
     nowbusy $view "Reading"
-    readrefs
-    changedrefs
     if {$showneartags} {
 	getallcommits
     }
@@ -579,7 +578,7 @@ proc insertrow {id p v} {
 
 proc removerow {id v} {
     global varcid varccommits parents children commitidx
-    global varctok vtokmod cmitlisted
+    global varctok vtokmod cmitlisted currentid selectedline
 
     if {[llength $parents($v,$id)] != 1} {
 	puts "oops: removerow [shortids $id] has [llength $parents($v,$id)] parents"
@@ -605,6 +604,10 @@ proc removerow {id v} {
     if {[string compare [lindex $varctok($v) $a] $vtokmod($v)] < 0} {
 	modify_arc $v $a $i
     }
+    if {[info exist currentid] && $id eq $currentid} {
+	unset currentid
+	unset selectedline
+    }
     drawvisible
 }
 
@@ -733,7 +736,7 @@ proc rowofcommit {id} {
 	return {}
     }
     set a $varcid($v,$id)
-    if {[string compare [lindex $varctok($v) $a] $vtokmod($v)] > 0} {
+    if {[string compare [lindex $varctok($v) $a] $vtokmod($v)] >= 0} {
 	update_arcrows $v
     }
     set i [lsearch -exact $varccommits($v,$a) $id]
@@ -3515,7 +3518,7 @@ proc dodiffindex {} {
 }
 
 proc readdiffindex {fd serial} {
-    global mainheadid nullid2 curview commitinfo commitdata lserial
+    global mainheadid nullid nullid2 curview commitinfo commitdata lserial
 
     set isdiff 1
     if {[gets $fd line] < 0} {
@@ -3541,6 +3544,9 @@ proc readdiffindex {fd serial} {
 	set hl [mc "Local changes checked in to index but not committed"]
 	set commitinfo($nullid2) [list  $hl {} {} {} {} "    $hl\n"]
 	set commitdata($nullid2) "\n    $hl\n"
+	if {[commitinview $nullid $curview]} {
+	    removerow $nullid $curview
+	}
 	insertrow $nullid2 $mainheadid $curview
     } elseif {!$isdiff && [commitinview $nullid2 $curview]} {
 	removerow $nullid2 $curview
@@ -5058,7 +5064,9 @@ proc selcanvline {w x y} {
 	set l 0
     }
     if {$w eq $canv} {
-	if {![info exists rowtextx($l)] || $x < $rowtextx($l)} return
+	set xmax [lindex [$canv cget -scrollregion] 2]
+	set xleft [expr {[lindex [$canv xview] 0] * $xmax}]
+	if {![info exists rowtextx($l)] || $xleft + $x < $rowtextx($l)} return
     }
     unmarkmatches
     selectline $l 1
@@ -5305,13 +5313,12 @@ proc selectline {l isnew} {
 
     make_secsel $l
 
+    set id [commitonrow $l]
     if {$isnew} {
-	addtohistory [list selectline $l 0]
+	addtohistory [list selbyid $id]
     }
 
     set selectedline $l
-
-    set id [commitonrow $l]
     set currentid $id
     $sha1entry delete 0 end
     $sha1entry insert 0 $id
@@ -6765,24 +6772,24 @@ proc domktag {} {
 }
 
 proc redrawtags {id} {
-    global canv linehtag idpos selectedline curview
+    global canv linehtag idpos currentid curview
     global canvxmax iddrawn
 
     if {![commitinview $id $curview]} return
     if {![info exists iddrawn($id)]} return
-    drawcommits [rowofcommit $id]
+    set row [rowofcommit $id]
     $canv delete tag.$id
     set xt [eval drawtags $id $idpos($id)]
-    $canv coords $linehtag([rowofcommit $id]) $xt [lindex $idpos($id) 2]
-    set text [$canv itemcget $linehtag([rowofcommit $id]) -text]
-    set xr [expr {$xt + [font measure mainfont $text]}]
+    $canv coords $linehtag($row) $xt [lindex $idpos($id) 2]
+    set text [$canv itemcget $linehtag($row) -text]
+    set font [$canv itemcget $linehtag($row) -font]
+    set xr [expr {$xt + [font measure $font $text]}]
     if {$xr > $canvxmax} {
 	set canvxmax $xr
 	setcanvscroll
     }
-    if {[info exists selectedline]
-	&& $selectedline == [rowofcommit $id]} {
-	selectline $selectedline 0
+    if {[info exists currentid] && $currentid == $id} {
+	make_secsel $row
     }
 }
 
@@ -8342,7 +8349,7 @@ proc changedrefs {} {
 }
 
 proc rereadrefs {} {
-    global idtags idheads idotherrefs mainhead
+    global idtags idheads idotherrefs mainheadid
 
     set refids [concat [array names idtags] \
 		    [array names idheads] [array names idotherrefs]]
@@ -8351,16 +8358,16 @@ proc rereadrefs {} {
 	    set ref($id) [listrefs $id]
 	}
     }
-    set oldmainhead $mainhead
+    set oldmainhead $mainheadid
     readrefs
     changedrefs
     set refids [lsort -unique [concat $refids [array names idtags] \
 			[array names idheads] [array names idotherrefs]]]
     foreach id $refids {
 	set v [listrefs $id]
 	if {![info exists ref($id)] || $ref($id) != $v ||
-	    ($id eq $oldmainhead && $id ne $mainhead) ||
-	    ($id eq $mainhead && $id ne $oldmainhead)} {
+	    ($id eq $oldmainhead && $id ne $mainheadid) ||
+	    ($id eq $mainheadid && $id ne $oldmainhead)} {
 	    redrawtags $id
 	}
     }