git-gui: Better document our blame variables

The array variable "order" used to be used to tell us in what
order each commit was received in.  Recent changes have removed
that need for an ordering and the "order" array is now just a
boolean 'do we have that commit yet' flag.

The colors were moved to fields, so they appear inside of the
blame viewer instance.  This keeps two different concurrently
running blame viewers from stepping on each other's ordering
of the colors in group_colors.

Most of the other fields were moved around a little bit so
that they are organized by major category and value lifespan.

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

lib/blame.tcl

@@ -5,10 +5,13 @@ class blame {
 
 image create photo ::blame::img_back_arrow -data {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}
 
-field commit    ; # input commit to blame
+# Persistant data (survives loads)
-field path      ; # input filename to view in $commit
+#
 field history {}; # viewer history: {commit path}
+field header    ; # array commit,key -> header field
 
+# Tk UI control paths
+#
 field w          ; # top window in this viewer
 field w_back     ; # our back button
 field w_path     ; # label showing the current file path
@@ -19,15 +22,27 @@ field w_cmit     ; # pane showing commit message
 field status     ; # text variable bound to status bar
 field old_height ; # last known height of $w.file_pane
 
+# Tk UI colors
+#
+field active_color #c0edc5
+field group_colors {
+	#d6d6d6
+	#e1e1e1
+	#ececec
+}
+
+# Current blame data; cleared/reset on each load
+#
+field commit               ; # input commit to blame
+field path                 ; # input filename to view in $commit
+
 field current_fd        {} ; # background process running
 field highlight_line    -1 ; # current line selected
 field highlight_commit  {} ; # sha1 of commit selected
 
 field total_lines       0  ; # total length of file
 field blame_lines       0  ; # number of lines computed
-field commit_count      0  ; # number of commits loaded
+field have_commit          ; # array commit -> 1
-field order                ; # array commit -> receipt order
-field header               ; # array commit,key -> header field
 field line_commit          ; # array line -> sha1 commit
 field line_file            ; # array line -> file name
 
@@ -41,15 +56,7 @@ field tooltip_timer  {} ; # Current timer event for our tooltip
 field tooltip_commit    {} ; # Commit in tooltip
 field tooltip_text      {} ; # Text in current tooltip
 
-variable active_color #c0edc5
-variable group_colors {
-	#d6d6d6
-	#e1e1e1
-	#ececec
-}
-
 constructor new {i_commit i_path} {
-	variable active_color
 	global cursor_ptr
 
 	set commit $i_commit
@@ -307,8 +314,7 @@ method _load {} {
 		set highlight_commit {}
 		set total_lines 0
 		set blame_lines 0
-		set commit_count 0
+		array unset have_commit
-		array unset order
 		array unset line_commit
 		array unset line_file
 
@@ -449,8 +455,6 @@ method _read_file {fd} {
 } ifdeleted { catch {close $fd} }
 
 method _read_blame {fd} {
-	variable group_colors
-
 	if {$fd ne $current_fd} {
 		catch {close $fd}
 		return
@@ -465,7 +469,7 @@ method _read_blame {fd} {
 			set r_final_line $final_line
 			set r_line_count $line_count
 
-			if {[catch {set g $order($cmit)}]} {
+			if {[catch {set g $have_commit($cmit)}]} {
 				set bg [lindex $group_colors 0]
 				set group_colors [lrange $group_colors 1 end]
 				lappend group_colors $bg
@@ -474,8 +478,7 @@ method _read_blame {fd} {
 				$w_line tag conf g$cmit -background $bg
 				$w_file tag conf g$cmit -background $bg
 
-				set order($cmit) $commit_count
+				set have_commit($cmit) 1
-				incr commit_count
 			}
 		} elseif {[string match {filename *} $line]} {
 			set file [string range $line 9 end]
@@ -635,7 +638,6 @@ method _load_commit {pos} {
 
 method _showcommit {lno} {
 	global repo_config
-	variable active_color
 
 	if {$highlight_commit ne {}} {
 		set cmit $highlight_commit