tests: allow Google's internal builds of clang-format to be used These builds do not actually include any Google-specific formatting changes; the only reason they don't include the LLVM version number is due to a decision to elide the version number from *all* LLVM/clang projects. For most builds of clang-format, even "unofficial" ones, the LLVM version will be displayed; example: ``` clang-format version 14.0.0 (https://github.com/llvm/llvm-project.git 1830ec94ac022ae0b6d6876fc2251e6b91e5931e) ``` The Google-internal build looks like this: ``` clang-format version google3-trunk (1830ec94ac022ae0b6d6876fc2251e6b91e5931e) ``` Differential Revision: https://phab.mercurial-scm.org/D10538

Set up

  $ hg init repo
  $ cd repo

Try to import an empty patch

  $ hg import --no-commit - <<EOF
  > EOF
  applying patch from stdin
  abort: stdin: no diffs found
  [10]

No dirstate backups are left behind

  $ ls .hg/dirstate* | sort
  .hg/dirstate