pub fn merge_default_cache_mounts(df: &mut Dockerfile, options: &BuildOptions)Expand description
Merge the build’s default cache mounts into every RUN instruction of a
Dockerfile IR, in place.
For each RUN instruction, every RunMount::Cache entry in
options.default_cache_mounts is appended to run.mounts unless a cache
mount with the same target is already present (step-level mounts win).
Non-cache entries in default_cache_mounts are ignored (the field only ever
carries cache mounts, but we filter defensively).
This lifts the auto-cache-mount injection that the buildah CLI backend used
to do inline per-RUN so it now materializes as real IR before rendering —
making the rendered Dockerfile carry the --mount=type=cache flags
identically for any backend that renders the IR to text.
A no-op when options.default_cache_mounts is empty (the common case).