+# Exit immediately if there are no diffs
+if test ! -s "$tmp/filelist"
+then
+ exit 0
+fi
+
+if test -n "$copy_back" && test "$right_dir" != "working_tree"
+then
+ echo "--copy-back is only valid when diff includes the working tree."
+ exit 1
+fi
+
+# Create the named tmp directories that will hold the files to be compared
+mkdir -p "$tmp/$left_dir" "$tmp/$right_dir"
+
+# Populate the tmp/right_dir directory with the files to be compared
+while read name
+do
+ if test -n "$right"
+ then
+ ls_list=$(git ls-tree $right "$name")
+ if test -n "$ls_list"
+ then
+ mkdir -p "$tmp/$right_dir/$(dirname "$name")"
+ git show "$right":"$name" >"$tmp/$right_dir/$name" || true
+ fi
+ elif test -n "$compare_staged"
+ then
+ ls_list=$(git ls-files -- "$name")
+ if test -n "$ls_list"
+ then
+ mkdir -p "$tmp/$right_dir/$(dirname "$name")"
+ git show :"$name" >"$tmp/$right_dir/$name"
+ fi
+ else
+ if test -e "$name"
+ then
+ mkdir -p "$tmp/$right_dir/$(dirname "$name")"
+ cp "$name" "$tmp/$right_dir/$name"
+ fi
+ fi
+done < "$tmp/filelist"
+
+# Populate the tmp/left_dir directory with the files to be compared
+while read name
+do
+ if test -n "$left"
+ then
+ ls_list=$(git ls-tree $left "$name")
+ if test -n "$ls_list"
+ then
+ mkdir -p "$tmp/$left_dir/$(dirname "$name")"
+ git show "$left":"$name" >"$tmp/$left_dir/$name" || true
+ fi
+ else
+ if test -n "$compare_staged"
+ then
+ ls_list=$(git ls-tree HEAD "$name")
+ if test -n "$ls_list"
+ then
+ mkdir -p "$tmp/$left_dir/$(dirname "$name")"
+ git show HEAD:"$name" >"$tmp/$left_dir/$name"
+ fi
+ else
+ mkdir -p "$tmp/$left_dir/$(dirname "$name")"
+ git show :"$name" >"$tmp/$left_dir/$name"
+ fi
+ fi
+done < "$tmp/filelist"
+
+LOCAL="$tmp/$left_dir"
+REMOTE="$tmp/$right_dir"
+
+if test -n "$diff_tool"
+then
+ export BASE
+ eval $diff_tool '"$LOCAL"' '"$REMOTE"'