+proc find_hunk_blamespec {base line} {
+ global ctext
+
+ # Find and parse the hunk header
+ set s_lix [$ctext search -backwards -regexp ^@@ "$line.0 lineend" $base.0]
+ if {$s_lix eq {}} return
+
+ set s_line [$ctext get $s_lix "$s_lix + 1 lines"]
+ if {![regexp {^@@@*(( -\d+(,\d+)?)+) \+(\d+)(,\d+)? @@} $s_line \
+ s_line old_specs osz osz1 new_line nsz]} {
+ return
+ }
+
+ # base lines for the parents
+ set base_lines [list $new_line]
+ foreach old_spec [lrange [split $old_specs " "] 1 end] {
+ if {![regexp -- {-(\d+)(,\d+)?} $old_spec \
+ old_spec old_line osz]} {
+ return
+ }
+ lappend base_lines $old_line
+ }
+
+ # Now scan the lines to determine offset within the hunk
+ set parent {}
+ set max_parent [expr {[llength $base_lines]-2}]
+ set dline 0
+ set s_lno [lindex [split $s_lix "."] 0]
+
+ for {set i $line} {$i > $s_lno} {incr i -1} {
+ set c_line [$ctext get $i.0 "$i.0 + 1 lines"]
+ # Determine if the line is removed
+ set chunk [string range $c_line 0 $max_parent]
+ set removed_idx [string first "-" $chunk]
+ # Choose a parent index
+ if {$parent eq {}} {
+ if {$removed_idx >= 0} {
+ set parent $removed_idx
+ } else {
+ set unchanged_idx [string first " " $chunk]
+ if {$unchanged_idx >= 0} {
+ set parent $unchanged_idx
+ } else {
+ # blame the current commit
+ set parent -1
+ }
+ }
+ }
+ # then count other lines that belong to it
+ if {$parent >= 0} {
+ set code [string index $c_line $parent]
+ if {$code eq "-" || ($removed_idx < 0 && $code ne "+")} {
+ incr dline
+ }
+ } else {
+ if {$removed_idx < 0} {
+ incr dline
+ }
+ }
+ }
+
+ if {$parent eq {}} { set parent -1 }
+ incr parent
+ incr dline [lindex $base_lines $parent]
+ return [list $parent $dline]
+}
+
+proc external_blame_diff {} {
+ global currentid diffmergeid cmitmode
+ global diff_menu_txtpos diff_menu_line
+ global diff_menu_filebase flist_menu_file
+
+ if {$cmitmode eq "tree"} {
+ set parent_idx 0
+ set line [expr {$diff_menu_line - $diff_menu_filebase - 1}]
+ } else {
+ set hinfo [find_hunk_blamespec $diff_menu_filebase $diff_menu_line]
+ if {$hinfo ne {}} {
+ set parent_idx [lindex $hinfo 0]
+ set line [lindex $hinfo 1]
+ } else {
+ set parent_idx 0
+ set line 0
+ }
+ }
+
+ external_blame $parent_idx $line
+}
+
+proc external_blame {parent_idx {line {}}} {