Document how to run crane via bazel run

[peakschris]

It seems like it should be possible to run rules_oci's crane via bazel run - but I can't figure out the command line

Any guidance would be greatly appreciated!

[willstranton]

Crane in this project is defined as a toolchain. I don't think you can directly bazel run a given toolchain's binary, but here's a quick genrule to pull out the binary:

genrule(
  name = "crane_bin",
  outs = ["crane"],
  cmd = "cp $(CRANE_BIN) $@",
  toolchains = ["@oci_crane_toolchains//:current_toolchain"],
  executable = True,
)

You can then bazel run :crane_bin to run crane.

The $(CRANE_BIN) is expanded from the toolchain definition here

You can see other uses of $(CRANE_BIN) under oci/tests/

[thesayyn]

Crane tool in rules_oci, is not part of the public api and will be removed in 3.0, so i would not recommend depending on it.