git diff check updated to watch for md changes

* Whenever the CLI usage is updated, it is required to run
  make cli-docs. So added that check in git-diff to capture in gates
  if missed by user

Change-Id: I47be48e921505593e745c11ce139f8079abc686a

tools/git_diff_check

@@ -23,6 +23,13 @@ then
     exit 1
 fi
 
+git diff-files --quiet --ignore-submodules **/*.md
+if [ $? -ne 0 ]
+then
+    echo "git diff found modified cli help, please run make cli-docs"
+    exit 1
+fi
+
 # Evaluate git index for differences, if found print message and fail.
 git diff-index --cached --quiet --ignore-submodules HEAD -- **/*.golden
 if [ $? -ne 0 ]
@@ -31,4 +38,11 @@ then
     exit 1
 fi
 
-echo "no git diff detected, make target completed successfully"
+git diff-index --cached --quiet --ignore-submodules HEAD -- **/*.md
+if [ $? -ne 0 ]
+then
+    echo "git diff found modified cli help, please run make cli-docs"
+    exit 1
+fi
+
+echo "no git diff detected, make target completed successfully"