identifiers: Expose manifest computation
Before this commit, manifests were only computed internally before hashing, so they were not available to outside modules.
This makes testing the module very painful, because identifier functions can only be tested by checking the hash; so test failures did not show mismatches between the computed manifest and the expected one.
Additionally, the 'git bare cooker' of the vault is likely to use these as well, as it needs to format git objects in the same format.
Test Plan
Should I add specific tests for the new manifest functions? They are indirectly tested by the existing tests.
Migrated from D5650 (view on Phabricator)