README makes it sound like only COPY and RUN layers can be cached, doesn't seem to be the case

[sh-at-cs]

The README currently says

kaniko can cache layers created by RUN (configured by flag --cache-run-layers) and COPY (configured by flag --cache-copy-layers) commands in a remote repository.

That makes it sound like only RUN and COPY layers can be cached, but when I try putting e.g. ENV or ADD statements before the RUN and COPY ones, the cache is consulted for the subsequent layers anyway. Whereas if ENV and ADD truly weren't cached at all, the cache would stop working, because as the README points out elsewhere:

Note that kaniko cannot read layers from the cache after a cache miss: once a layer has not been found in the cache, all subsequent layers are built locally without consulting the cache.

So IMHO there should be more details about how the cache interacts with non-COPY/non-RUN layers.

Related issue (regarding the same sentence, but a different aspect of it): #1940