Improve documentation on what to do with containers/image failures in…

… test-skopeo

README.md

@@ -184,10 +184,20 @@ In order to update an existing dependency:
 - update the relevant dependency line in `vendor.conf`
 - run `vndr github.com/pkg/errors`
 
-In order to test out new PRs from [containers/image](https://github.com/containers/image) to not break `skopeo`:
+When new PRs for [containers/image](https://github.com/containers/image) break `skopeo` (i.e. `containers/image` tests fail in `make test-skopeo`):
 
+- create out a new branch in your `skopeo` checkout and switch to it
 - update `vendor.conf`. Find out the `containers/image` dependency; update it to vendor from your own branch and your own repository fork (e.g. `github.com/containers/image my-branch https://github.com/runcom/image`)
 - run `vndr github.com/containers/image`
+- make any other necessary changes in the skopeo repo (e.g. add other dependencies now requied by `containers/image`, or update skopeo for changed `containers/image` API)
+- optionally add new integration tests to the skopeo repo
+- submit the resulting branch as a skopeo PR, marked “DO NOT MERGE”
+- iterate until tests pass and the PR is reviewed
+- then the original `containers/image` PR can be merged, disregarding its `make test-skopeo` failure
+- as soon as possible after that, in the skopeo PR, restore the `containers/image` line in `vendor.conf` to use `containers/image:master`
+- run `vndr github.com/containers/image`
+- update the skopeo PR with the result, drop the “DO NOT MERGE” marking
+- after tests complete succcesfully again, merge the skopeo PR
 
 License
 -