Add a code formatting script

Add a code formatting script derived from the one provided in the
Babeltrace tree.

Change-Id: Idaf127ac199d1783769b7fe6a3216113bd9b7e83
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/format-cpp b/format-cpp
new file mode 100755 (executable)
index 0000000..a610728
--- /dev/null
+++ b/format-cpp
@@ -0,0 +1,56 @@
+#!/bin/bash
+#
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Copyright (C) 2020-2022 Philippe Proulx <pproulx@efficios.com>
+
+expected_formatter_major_version=14
+
+# Runs the formatter, making sure it's the expected version.
+format_cpp() {
+       local formatter=$1
+       local version
+
+       version=$($formatter --version)
+
+        # shellcheck disable=SC2181
+       if (($? != 0)); then
+               echo "Cannot execute \`$formatter --version\`." >&2
+               return 1
+       fi
+
+       if [[ "$version" != *"clang-format version $expected_formatter_major_version"* ]]; then
+               echo "Expecting clang-format $expected_formatter_major_version." >&2
+               echo -n Got: >&2
+               echo " \`$version\`" >&2
+               echo >&2
+               echo "Use the FORMATTER environment variable to specify the location of clang-format $expected_formatter_major_version"
+               return 1
+       fi
+
+       local root_dir
+
+       root_dir="$(dirname "${BASH_SOURCE[0]}")"
+
+       # Using xargs to fail as soon as the formatter fails (`-exec`
+       # won't stop if its subprocess fails).
+       #
+       # shellcheck disable=SC2086
+       find "$root_dir" -path './src/vendor' -prune \
+               -o -type f \( -name '*\.h' -o -name '*\.hpp' -o -name '*\.c' -o -name '*\.cpp' \) \
+               -not -path '*/\.*' -print0 | xargs -n1 -0 $formatter -i --style=file --fallback-style=none
+}
+
+if [[ -n "$FORMATTER" ]]; then
+       # Try using environment-provided formatter
+       formatter=$FORMATTER
+elif command -v clang-format-$expected_formatter_major_version &> /dev/null; then
+       # Try using the expected version of clang-format
+       formatter="clang-format-$expected_formatter_major_version -i"
+else
+       # Try using `clang-format` as is
+       formatter='clang-format -i'
+fi
+
+# Try to format files
+format_cpp "$formatter"