Add a .clang-format file and helper tool

It won't automatically be enforced, but should be picked up by editors
that support it (such as VS code + CPP extension)

It doesn't yet follow project style entirely, so more tweaking is
likely needed.

Also add a helper tool for reformatting new files to match project style

.clang-format

@@ -0,0 +1,44 @@
+---
+AlignAfterOpenBracket: 'Align'
+AlignConsecutiveAssignments: 'false'
+AlignConsecutiveDeclarations: 'true'
+AlignConsecutiveMacros: 'true'
+AlignOperands: 'true'
+AlignTrailingComments: 'true'
+AllowAllParametersOfDeclarationOnNextLine: 'false'
+AllowShortBlocksOnASingleLine: 'false'
+AllowShortCaseLabelsOnASingleLine: 'false'
+AllowShortFunctionsOnASingleLine: 'Inline'
+AllowShortIfStatementsOnASingleLine: 'false'
+AlwaysBreakAfterReturnType: 'All'
+BinPackParameters: 'false'
+BinPackArguments: 'true'
+BreakBeforeBraces: 'Linux'
+DerivePointerAlignment: 'false'
+IndentCaseLabels: 'false'
+IndentWidth: '8'
+IncludeBlocks: 'Regroup'
+KeepEmptyLinesAtTheStartOfBlocks: 'false'
+Language: 'Cpp'
+MaxEmptyLinesToKeep: '1'
+PointerAlignment: 'Right'
+SortIncludes: 'true'
+SpaceAfterCStyleCast: 'true'
+SpaceBeforeAssignmentOperators : 'true'
+SpaceBeforeParens: 'Always'
+SpaceInEmptyParentheses: 'false'
+SpacesInSquareBrackets: 'false'
+TabWidth: '8'
+UseTab: 'Always'
+
+PenaltyBreakAssignment: '3'
+PenaltyBreakString: '10'
+PenaltyExcessCharacter: '1'
+PenaltyBreakBeforeFirstCallParameter: '15'
+
+IncludeCategories:
+  - Regex:           'config.h'
+    Priority:        '0'
+  - Regex:           '.*'
+    Priority:        '1'
+...

contrib/reformat-code.py

@@ -0,0 +1,80 @@
+#!/usr/bin/python3
+#
+# Copyright (C) 2017 Dell Inc.
+#
+# SPDX-License-Identifier: LGPL-2.1+
+#
+
+import argparse
+import os
+import sys
+import subprocess
+
+CLANG_FORMATTERS = [
+    "clang-format-13",
+    "clang-format",
+]
+FIXUPS = {"g_autoptr (": "g_autoptr(", "sizeof (": "sizeof(", "g_auto (": "g_auto("}
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(description="Reformat code to match style")
+    parser.add_argument("files", nargs="*", help="files to reformat")
+    args = parser.parse_args()
+    if len(args.files) == 0:
+        parser.print_help()
+        sys.exit(0)
+    return args
+
+
+def select_clang_version():
+    for formatter in CLANG_FORMATTERS:
+        try:
+            ret = subprocess.check_call([formatter, "--version"])
+            if ret == 0:
+                return formatter
+        except FileNotFoundError:
+            continue
+    return None
+
+
+def reformat_file(formatter, f):
+    print("Reformatting %s using %s" % (f, formatter))
+    lines = None
+    with open(f, "r") as rfd:
+        lines = rfd.readlines()
+    ret = subprocess.run(
+        [formatter, "-style=file", f], capture_output=True, check=True, text=True
+    )
+    if ret.returncode:
+        print("Failed to run formatter")
+        sys.exit(1)
+    formatted = ret.stdout.splitlines(True)
+    save = False
+    for idx, line in enumerate(formatted):
+        for fixup in FIXUPS:
+            if fixup in line:
+                formatted[idx] = line.replace(fixup, FIXUPS[fixup])
+        if not save and formatted[idx] != lines[idx]:
+            save = True
+    if save:
+        with open(f, "w") as wfd:
+            wfd.writelines(formatted)
+
+
+## Entry Point ##
+if __name__ == "__main__":
+    args = parse_args()
+    formatter = select_clang_version()
+    if not formatter:
+        print("No clang formatter installed")
+        sys.exit(1)
+    for f in args.files:
+        if not os.path.exists(f):
+            print("%s does not exist" % f)
+            sys.exit(1)
+        if not (f.endswith(".c") or f.endswith(".h")):
+            print("Skipping %s" % f)
+            continue
+        reformat_file(formatter, f)
+    sys.exit(0)