What does - |- mean in yaml patch file

Question

In this example (link), it creates kind cluster with config file, which patch containerd. What does the - |- under the line of containerdConfigPatches mean?

I found - | in yaml indicates this is a patch field. But what does the - following - | mean?

# create a cluster with the local registry enabled in containerd
cat <<EOF | kind create cluster --config=-
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
containerdConfigPatches:
- |-
  [plugins."io.containerd.grpc.v1.cri".registry.mirrors."localhost:${reg_port}"]
    endpoint = ["http://${reg_name}:5000"]
EOF

Answer 1

|- introduces a YAML block scalar, a way of writing a multi-line string. The | means that newlines are preserved (> would fold the string into a single line), and the - means the new line at the end is removed.

anywhere: |-
  This is a multi-line string.  The new
  line in the middle is preserved.

The - at the start of the line (the space is important) is a YAML block sequence (list). This is the same way other lists are presented; for example

listOfStrings:
  - one
  - two
  - three

The - |- is nothing more than combining these two things: it is a list item whose value is a multi-line string.