The "hash-policy" command:

Usage: fossil hash-policy ?NEW-POLICY?

Query or set the hash policy for the current repository. Available hash policies are as follows:

sha1

New artifact names are created using SHA1

auto

New artifact names are created using SHA1, but automatically change the policy to "sha3" when any SHA3 artifact enters the repository.

sha3

New artifact names are created using SHA3, but older artifacts with SHA1 names may be reused.

sha3-only

Use only SHA3 artifact names. Do not reuse legacy SHA1 names.

shun-sha1

Shun any SHA1 artifacts received by sync operations other than clones. Older legacy SHA1 artifacts are allowed during a clone.

The default hash policy for existing repositories is "auto", which will immediately promote to "sha3" if the repository contains one or more artifacts with SHA3 names. The default hash policy for new repositories is "shun-sha1".