COPY --from should reference a previously defined FROM alias.
Description
When using multi-stage builds,COPY --from should reference a stage alias that was previously defined with FROM ... AS <alias>. Trying to copy
from a missing image alias results in an error at build time.
Why default Off
This rule is off by default because it does not account for--build-context
sources. As per the official Dockerfile documentation:
You can also copy files directly from named contexts
(specified with --build-context <name>=<source>) or images.
Since named build contexts are supplied at build time (docker buildx build --build-context name=path), a static linter cannot verify whether a
COPY --from=name reference is valid. Flagging these as violations produces
false positives that cannot be resolved without running the actual build.
To enable this rule, set its severity explicitly in your .tally.toml: