adds our clang-format script and config

config

+# all key value pairs get set in the module local
+# git config by dunecontrol
+hooks.clangformat clang-format-3.8

hooks/pre-commit

+#!/usr/bin/env python3
+
+"""
+    This pre-commit hook checks each staged file if it complies to the
+    formatting rules, as defined by clang-format (or the programm specified
+    in `git config hooks.clangformat`).
+"""
+
+import os
+import subprocess
+import sys
+import tempfile
+
+CPP_EXTENSIONS = ('.c', '.cc', '.cxx', '.h', '.hh', '.hxx', '.pbh')
+
+
+class FormatRunException(RuntimeError):
+    pass
+
+
+class NonEmptyDiffException(Exception):
+    pass
+
+
+def check_dir(basedir, mode='staged'):
+    """
+    :param basedir: absolute path to git root
+    :param mode: anyof 'staged', 'modified' or 'all' to select which files to check. Note
+                    staged files do not count as modified
+    :return: list of filename with non-empty diff to current state after applying clang-format
+    """
+    commands = {'staged': ['git', 'diff', '--name-only', '--cached'],
+                'modified': ['git', 'ls-files', '-m'],
+                'all': ['git', 'ls-files']}
+    os.chdir(basedir)
+    # alternative clang-format binary given?
+    try:
+        clangformat = subprocess.check_output(['git', 'config', 'hooks.clangformat'],
+                                              universal_newlines=True).strip()
+    except subprocess.CalledProcessError as _:
+        clangformat = 'clang-format'
+
+    out = subprocess.check_output(commands[mode],
+                                  universal_newlines=True)
+    fails = []
+    for changed_file in sorted(out.splitlines()):
+        try:
+            check_file(changed_file, basedir, clangformat)
+        except NonEmptyDiffException:
+            fails.append(changed_file)
+    return fails
+
+
+def check_file(touched_file, basedir, format_binary, extension_whitelist=CPP_EXTENSIONS):
+    if os.path.splitext(touched_file)[1] not in extension_whitelist:
+        return
+    filename = os.path.join(basedir, touched_file)
+
+    try:
+        out = subprocess.check_output([format_binary, '-style=file', filename],
+                                    universal_newlines=True)
+    except subprocess.CalledProcessError as e:
+        raise FormatRunException('Error executing {} on file\n{}'.format(format_binary, filename, e.output))
+    tmp_filename = tempfile.NamedTemporaryFile(mode='wb', delete=False).name
+    with open(tmp_filename, 'w') as tmp_file:
+        tmp_file.write(out)
+    try:
+        subprocess.check_output(['diff', filename, tmp_filename],
+                                      universal_newlines=True)
+    except subprocess.CalledProcessError as res:
+        if res.returncode == 1:
+            raise NonEmptyDiffException('clang-format has to be applied to \'{}\'!'.format(filename))
+        raise RuntimeError('error diffing {} vs {}'.format(touched_file, tmp_filename))
+    finally:
+        os.remove(tmp_filename)
+
+if __name__ == '__main__':
+    dirname = os.path.abspath(sys.argv[1] if len(sys.argv) > 1 else os.getcwd())
+    fails = check_dir(dirname, mode='staged')
+    if len(fails) > 0:
+        print('files need to be formatted:\n\t{}'.format('\n\t'.join(fails)) )
+    sys.exit(len(fails))