[clang] [clang-format] Add null-terminated path option (#123921) (PR #123926)

[Nikolaos Chatzikonstantinou via cfe-commits]

createyourpersonalaccount wrote:

> This seems reasonable to me, but wait for the others, maybe @owenca

I'm wondering if `-0` should turn off all informational messaging as well and *only* print the paths. As it is, it will print things like _Running clang-format on the following files:_, even if a null-separated list of files follows.

So right now the usage would be (example)

```sh
git clang-format --staged -z | tail -n +2 | xargs -0 git add
```

but perhaps it should not print informational messages and have the usage be simplified:

```sh
git clang-format --staged -z | xargs -0 git add
```

https://github.com/llvm/llvm-project/pull/123926