git-gui: Correct ls-tree buffering problem in browser

Our file browser was showing bad output as it did not properly buffer
a partial record when read from `ls-tree -z`.  This did not show up on
my Mac OS X system as most trees are small, the pipe buffers generally
big and `ls-tree -z` was generally fast enough that all data was ready
before Tcl started to read.  However on my Cygwin system one of my
production repositories had a large enough tree and packfile that it
took a couple of pipe buffers for `ls-tree -z` to complete its dump.

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

lib/browser.tcl

@@ -11,6 +11,8 @@ field browser_status {Starting...}
 field browser_stack  {}
 field browser_busy   1
 
+field ls_buf     {}; # Buffered record output from ls-tree
+
 constructor new {commit} {
 	global cursor_ptr M1B
 	make_toplevel top w
@@ -160,7 +162,7 @@ method _click {was_double_click pos} {
 }
 
 method _ls {tree_id {name {}}} {
-	set browser_buffer {}
+	set ls_buf {}
 	set browser_files {}
 	set browser_busy 1
 
@@ -185,17 +187,19 @@ method _ls {tree_id {name {}}} {
 }
 
 method _read {fd} {
-	append browser_buffer [read $fd]
-	set pck [split $browser_buffer "\0"]
-	set browser_buffer [lindex $pck end]
+	append ls_buf [read $fd]
+	set pck [split $ls_buf "\0"]
+	set ls_buf [lindex $pck end]
 
 	set n [llength $browser_files]
 	$w conf -state normal
 	foreach p [lrange $pck 0 end-1] {
-		set info [split $p "\t"]
-		set path [lindex $info 1]
-		set info [split [lindex $info 0] { }]
-		set type [lindex $info 1]
+		set tab [string first "\t" $p]
+		if {$tab == -1} continue
+
+		set info [split [string range $p 0 [expr {$tab - 1}]] { }]
+		set path [string range $p [expr {$tab + 1}] end]
+		set type   [lindex $info 1]
 		set object [lindex $info 2]
 
 		switch -- $type {
@@ -225,7 +229,7 @@ method _read {fd} {
 		close $fd
 		set browser_status Ready.
 		set browser_busy 0
-		unset browser_buffer
+		set ls_buf {}
 		if {$n > 0} {
 			$w tag add in_sel 1.0 2.0
 			focus -force $w