Current problems:
- bash(1) is not always installed (by default), /bin/sh is
- (Open)BSD find(1) requires at least one path argument, i.e. `.` which GNU
find(1) implies
- (Open)BSD find(1) does not support `-ipath`
git-ls-files(1) benefits:
- gitignore(5) files are honored
- simpler/more powerful patterns (see gitglossary(7) wrt. `pathspec`)
- `runClangFormat.sh` can be run from git subdirectories to only format
selected files (explicitl passing files could be easil implemented)
- works on every system with git(1), no portability issues (see above)
The one "drawback" with git-ls-files(1) is requiring git(1) working tree
rather than a release tarball, but active development requries git
anyway, so that does not seem like a blocker.
Only run xargs(1) if files were listed (`-r`), since we can now run the
script from subdirectories without source code.
Avoid brace expansion (`'**/*'.{cpp,c,hpp,h,cxx,cc}`) to be compatible
with dash.
The used .clang-format file has been generated using clang-format 6
(shipped with Ubuntu 18.04) and is therefore backwards compatible with
all clang-format versions until v6.
