feat: add initial implementation

.gitignore

@@ -34,4 +34,5 @@ release/
 
 # Local testing files
 
-.secrets.env 
+.secrets.env
+*~

DOCS.md

@@ -1,5 +1,102 @@
 ## Description
 
-TODO: FILL ME
+This plugin enables you to build and publish [Docker Manifest List](https://www.docker.com/)
+or [OCI Image Index](https://github.com/opencontainers/image-spec/blob/main/image-index.md)
+in a Vela pipeline.
+
+Source Code: https://github.com/go-vela/vela-manifest-tool
+
+Registry: https://hub.docker.com/r/target/vela-manifest-tool
+
+## Usage
+
+> **NOTE:**
+>
+> Users should refrain from using latest as the tag for the Docker image.
+>
+> It is recommended to use a semantically versioned tag instead.
+
+Sample of building and publishing an image:
+
+```yaml
+steps:
+  - name: publish_hello-world
+    image: target/vela-manifest-tool:latest
+    pull: always
+    parameters:
+      registry: index.docker.io
+      repo: /octocat/hello-world
+      tags: [ "latest" ]
+      platforms:
+        - linux/amd64
+        - linux/arm64/v8
+      component_template: /octocat/hello-world:latest-{{ .Os }}-{{ .Arch }}{{ if .Variant }}-{{ .Variant }}{{ end }}
+```
+
+NOTE: For vela-manifest-tool, unlike for vela-kaniko, the `repo` argument excludes the `registry` value. Said another
+way, rather than using:
+
+```yaml
+parameters:
+  registry: index.docker.io
+  repo: index.docker.io/octocat/hello-world
+  ...
+  component_template: index.docker.io/octocat/hello-world:latest-{{ .Os }}-{{ .Arch }}{{ if .Variant }}-{{ .Variant }}{{ end }} 
+```
+
+You must instead use:
+
+```yaml
+parameters:
+  registry: index.docker.io
+  repo: /octocat/hello-world
+  ...
+  component_template: /octocat/hello-world:latest-{{ .Os }}-{{ .Arch }}{{ if .Variant }}-{{ .Variant }}{{ end }}
+```
+
+This is because manifest tool requires that all image repos referenced exist within the same registry. Resulting tags will
+all be the concatenation of the registry with the repo.
+
+Sample of building an image without publishing:
+
+```yaml
+steps:
+  - name: publish_hello-world
+    image: target/vela-manifest-tool:latest
+    pull: always
+    parameters:
++     dry_run: true
+      registry: index.docker.io
+      repo: /octocat/hello-world
+      tags: [ "latest" ]
+      platforms:
+        - linux/amd64
+        - linux/arm64/v8
+      component_template: /octocat/hello-world:latest-{{ .Os }}-{{ .Arch }}{{ if .Variant }}-{{ .Variant }}{{ end }}
+```
+
+For every element of `tags:`, one spec file will be generated and (unless `dry_run: true`) pushed to the `registry:`.
+For each manifest-tool spec file, the tag for the manifest list/image index will be `$registry$repo:$tag`. Then there will
+be one element   in the `manifests:` list of the spec file for each element of the `platform:` argument. Platform is assumed
+to be in `os/architecture/variant` format. Within the `component_template`, you can use Os, Arch, Variant (from the platform),
+or Tag (from the top level `tags:`).
+
+Note: The default component_template of `"{{.Repo}}:{{.Tag}}-{{.Os}}-{{.Arch}}{{if .Variant}}-{{.Variant}}{{end}}"` might
+be sufficient for most needs if you follow that tagging convention. For example, if the builds for /octocat/hello-world created
+the architecture specific image
+
+- index.docker.io/octocat/hello-world:latest-linux-amd64
+- index.docker.io/octocat/hello-world:latest-linux-arm64-v8
+
+Then the following configuration would be sufficient due to defaults for tags, platforms, and component_template:
+
+```yaml
+steps:
+  - name: publish_hello-world
+    image: target/vela-manifest-tool:latest
+    pull: always
+    parameters:
+      registry: index.docker.io
+      repo: /octocat/hello-world
+```
 
-see: https://github.com/go-vela/vela-kaniko/blob/main/DOCS.md

Dockerfile

@@ -0,0 +1,25 @@
+# SPDX-License-Identifier: Apache-2.0
+
+################################################################################
+##    docker build --no-cache --target certs -t vela-manifest-tool:certs .    ##
+################################################################################
+
+FROM alpine:3.19.1@sha256:c5b1261d6d3e43071626931fc004f70149baeba2c8ec672bd4f27761f8e1ad6b as certs
+
+RUN apk add --update --no-cache ca-certificates
+
+#################################################################
+##    docker build --no-cache -t vela-manifest-tool:local .    ##
+#################################################################
+
+FROM mplatform/manifest-tool:alpine-v2.1.6@sha256:96db9e944c50a5f7514394af4e44f764725645cfd2efef92d87095b0016a55ae
+
+COPY --from=certs /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
+
+WORKDIR /workspace
+
+RUN mkdir /root/.docker
+
+COPY release/vela-manifest-tool /bin/vela-manifest-tool
+
+ENTRYPOINT [ "/bin/vela-manifest-tool" ]