* use a virtual fat filesystem during the test
* this makes the file I/O part more closely patch runtime which is nice
* side-steps the need to add a special function for testing
* but test still can't be run on a device, because the vfs calls
are incompatible, and you intentionally can't remount "/" anyway
* and side-steps problems with storing 'bad' toml files
This adds the "no-run-if-empty" flag to the xargs invocation. Otherwise,
if git diff names no files, the command is run once with no agument
specified which leads to running on a default list of files that appears
to include ignored files and files in submodules.
I am uneasy about how this works (it means that `pre-commit run --all`
doesn't actually check all files) but that's a separate issue.