t / t5100 / patch0009on commit t3427: accommodate for the `rebase --merge` backend having been replaced (f67336d)
   1diff --git a/Documentation/diff-format.txt b/Documentation/diff-format.txt
   2index b426a14..97756ec 100644
   3--- a/Documentation/diff-format.txt
   4+++ b/Documentation/diff-format.txt
   5@@ -81,7 +81,7 @@ The "diff" formatting options can be customized via the
   6 environment variable 'GIT_DIFF_OPTS'.  For example, if you
   7 prefer context diff:
   8 
   9-      GIT_DIFF_OPTS=-c git-diff-index -p $(cat .git/HEAD)
  10+      GIT_DIFF_OPTS=-c git-diff-index -p HEAD
  11 
  12 
  13 2. When the environment variable 'GIT_EXTERNAL_DIFF' is set, the