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
$ for i in aaa zzz; do
> hg init t
> cd t
>
> echo
> echo "-- With $i"
>
> touch file
> hg add file
> hg ci -m "Add"
>
> hg cp file $i
> hg ci -m "a -> $i"
>
> hg cp $i other-file
> echo "different" >> $i
> hg ci -m "$i -> other-file"
>
> hg cp other-file somename
>
> echo "Status":
> hg st -C
> echo
> echo "Diff:"
> hg diff -g
>
> cd ..
> rm -rf t
> done
-- With aaa
Status:
A somename
other-file
Diff:
diff --git a/other-file b/somename
copy from other-file
copy to somename
-- With zzz
Status:
A somename
other-file
Diff:
diff --git a/other-file b/somename
copy from other-file
copy to somename