What is the .exemplar_version file for?

[ClausKlein]

just an small snapshot:

bash-5.3$ cd ..
bash-5.3$ head */.exemplar_version 
==> scan_view/.exemplar_version <==
07a42c8a3ace7b889d4d98df8f9ec3a4cf74887f

==> transform_view/.exemplar_version <==
07a42c8a3ace7b889d4d98df8f9ec3a4cf74887f

==> utf_view/.exemplar_version <==
a8a97fdec16bfd081aa1814402f13b6a20327046
bash-5.3$ 

see too steve-downey#6 (comment)