.ci/format/apply_shfmt.sh: introduced file

.ci/format/apply_shfmt.sh

+#!/bin/bash
+
+if [ -z "${SHFMT_BIN}" ]; then
+    SHFMT_BIN="shfmt"
+fi
+
+if ! command -v "${SHFMT_BIN}" >/dev/null 2>&1; then
+    echo "ERROR: Binary '${SHFMT_BIN}' does not exist, please set the environment variable SHFMT_BIN to the correct shfmt version."
+    exit 1
+fi
+
+format_command="${SHFMT_BIN} -w -i 4"
+
+apply_format_script="$(dirname "${BASH_SOURCE[0]}")/apply_format.sh"
+
+files_regex=".*\.sh$"
+
+if ! "${apply_format_script}" --format-command "${format_command}" --files-regex "${files_regex}" "$@"; then
+    echo "ERROR: Executing '${apply_format_script}' failed."
+    exit 1
+fi