doc: init nomad autodiscovery plugin documentation (#2151)

* fix: add missing updatecli/values.d/releasepost.yaml

* doc: init nomad autodiscovery plugin documentation

* fix: cleanup local file changes

Author: olblak

assets/code_example/docs/plugins/autodiscovery/nomad/updatecli.d/default.yaml

@@ -0,0 +1,33 @@
+name: "Nomad autodiscovery using GitHub"
+scms:
+  default:
+    kind: github
+    spec:
+      owner: updatecli-test
+      repository: nomad-demo
+      token: '{{ requiredEnv "GITHUB_TOKEN" }}'
+      username: '{{ requiredEnv "GITHUB_ACTOR" }}'
+      branch: master
+ 
+actions:
+  default:
+    scmid: default
+    kind: github/pullrequest
+    spec:
+      labels:
+        - "dependencies"
+
+autodiscovery:
+  scmid: default
+  actionid: default
+  crawlers:
+    nomad:
+      ignore:
+        - path: 'services/cache.nomad'
+      #   jobs:
+      #    -  traefik
+      # only:
+      #  # - path: <filepath relative from the scm repository>
+      #      jobs: <Nomad job name to match>
+      #      image: <docker image to match>
+

content/en/docs/plugins/autodiscovery/nomad.adoc

@@ -0,0 +1,89 @@
+---
+title: "Nomad"
+description: "Discover Docker image tag update from Nomad job files"
+lead: "kind: nomad"
+draft: false
+images: []
+menu:
+  docs:
+    parent: "plugin-autodiscovery"
+weight: 130
+toc: true
+plugins:
+  - autodiscovery
+---
+
+== Description
+
+The Nomad crawler looks recursively for all Nomad manifests from a specific root directory.
+Then, for each of them, it tries to update each Docker image tag found.
+
+Updatecli looks for the following file patterns:
+
+* `*.nomad`
+* `*.hcl`
+
+The automatic discovery behavior can be tuned by providing a YAML manifest with a `nomad` crawler in top-level directive `autodiscovery` as explained in the link:/docs/core/autodiscovery/#_parameters["Autodiscovery" page].
+
+=== Usage
+
+The nomad autodiscovery can use with or without manifest.
+
+**Without manifest**
+
+Without manifest available, Updatecli will enable all default crawlers, including nomad.
+
+`updatecli diff` to run updatecli in dryrun
+`updatecli apply` to apply the changes locally
+
+**With a manifest**
+
+If a manifest is provided, Updatecli will only execute crawlers specified in the manifest such as in the following example
+
+
+* `updatecli diff --config updatecli.d/default.yaml` to run updatecli in dryrun
+* `updatecli apply --config updatecli.d/default.yaml` to apply the changes
+
+[source,yaml]
+----
+# updatecli.d/default.yaml
+{{<include "assets/code_example/docs/plugins/autodiscovery/nomad/updatecli.d/default.yaml">}}
+----
+
+== Manifest
+
+=== Parameters
+
+{{< autodiscoveryparameters "nomad" >}}
+
+=== Docker Image Tag
+
+The Docker ecosystem has no versioning guidelines. This means that it's the wild west out there and pretty much impossible to detect all cases. Hence why Updatecli manifest was created.
+
+That being said we are still interested in an autodiscovery feature that would detect as many cases as possible.
+This section is about documentation what is covered and what's missing.
+Do not hesitate to look at the contributing section
+
+**Semantic Versioning**
+
+In the Docker ecosystem, many tags look like semver but are not.
+For instance, `node:18.12.1-alpine` would match the semver regular expression but the prerelease `-alpine` is not a prerelease information as per semver convention but a variant of `node:18.12.1-buster` or `node:18.12.1`.
+This means that we would expect a newer version with the `-alpine` such as `node:19.0.0-alpine`.
+
+The docker-compose autodiscovery will handle the following scenarios
+
+* `1` will suggest a version such `2` otherwise stick to `1`
+* `1-alpine` will suggest a version such `2-alpine` otherwise stick to `1-alpine`
+* `1.0` will suggest a version such `2.1` otherwise stick to `1.0`
+* `1.0-alpine` will suggest a version such `2.1-alpine` otherwise stick to `1.0-alpine`
+* `1.0.0` will suggest a version such `2.1.0` otherwise stick to `1.0.0`
+* `1.0.0-alpine` will suggest a version such `2.1.0-alpine` otherwise stick to `1.0.0-alpine`
+
+Any other version pattern such as PEP 440 are ignored in the current state.
+We are planning to add new versionFilter kinds in the future as the need raise.
+
+Feel free to:
+
+1. Open an link:https://github.com/updatecli/updatecli/issues/new/choose[issue] explaining the version pattern you are looking for.
+2. Add a `+1` to an existing link:https://github.com/updatecli/updatecli/issues[issue] as it helps us to prioritise
+3. Contribute to an existing one as it will move things faster.