git-gui: fix applying line/ranges when the selection ends at the begin of a line

Selecting also the trailing newline of a line for staging/unstaging would
have resulted in also staging/unstaging of the next line.

Signed-off-by: Bert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: Johannes Sixt <j6t@kdbg.org>

Author: bertwesarg

lib/diff.tcl

@@ -676,7 +676,13 @@ proc apply_or_revert_range_or_line {x y revert} {
 	}
 
 	set first_l [$ui_diff index "$first linestart"]
-	set last_l [$ui_diff index "$last lineend"]
+	# don't include the next line if $last points to the start of a line
+	# ie. <lno>.0
+	if {[lindex [split $last .] 1] == 0} {
+		set last_l [$ui_diff index "$last -1 line lineend"]
+	} else {
+		set last_l [$ui_diff index "$last lineend"]
+	}
 
 	if {$current_diff_path eq {} || $current_diff_header eq {}} return
 	if {![lock_index apply_hunk]} return