Enable the base branch to be overridden in the code format check script (#2607)

Default to master.

Signed-off-by: Kevin Petit <kevin.petit@arm.com>

utils/check_code_format.sh

@@ -18,14 +18,16 @@
 #
 # This script assumes to be invoked at the project root directory.
 
-FILES_TO_CHECK=$(git diff --name-only master | grep -E ".*\.(cpp|cc|c\+\+|cxx|c|h|hpp)$")
+BASE_BRANCH=${1:-master}
+
+FILES_TO_CHECK=$(git diff --name-only ${BASE_BRANCH} | grep -E ".*\.(cpp|cc|c\+\+|cxx|c|h|hpp)$")
 
 if [ -z "${FILES_TO_CHECK}" ]; then
   echo "No source code to check for formatting."
   exit 0
 fi
 
-FORMAT_DIFF=$(git diff -U0 master -- ${FILES_TO_CHECK} | python ./utils/clang-format-diff.py -p1 -style=file)
+FORMAT_DIFF=$(git diff -U0 ${BASE_BRANCH} -- ${FILES_TO_CHECK} | python ./utils/clang-format-diff.py -p1 -style=file)
 
 if [ -z "${FORMAT_DIFF}" ]; then
   echo "All source code in PR properly formatted."