cmake-format added support for reading from/outputting to stdin/out as
of v0.3.6, released 2018-04-10 (commit 2e2aff2) [0].
Reading from stdin is preferable over reading from a temporary file
because when given a concrete file cmake-format will look for its config
file (.cmake-format.py or similar) in the parent directories of the
provided file. If the temporary file is off in a tmpdir somewhere (e.g.,
/tmp on *nix), cmake-format will almost certainly not come across the
user's intended format configuration file, making it appear that
cmake-format is ignoring the config file.
If cmake-format reads from stdin, though, it'll look for its config file
in its current working directory and its parent directories, in a
similar manner to clang-format. This has a much higher chance of running
across the intended config file.
[0]: https://github.com/cheshirekow/cmake_format/releases/tag/v0.3.6
Co-authored-by: Alex Wang <ts826848@gmail.com>