docs(datasource): Add additional examples for custom datasource

lib/modules/datasource/custom/readme.md

@@ -82,7 +82,7 @@ All available options:
 
 ## Examples
 
-# K3s
+### K3s
 
 You can use this configuration to request the newest version available to [K3s](https://k3s.io/)
 
@@ -98,3 +98,95 @@ You can use this configuration to request the newest version available to [K3s](
   },
 }
 ```
+
+### Hashicorp
+
+You can use this configuration to request the newest versions of the Hashicorp products:
+
+```json5
+{
+  "regexManagers": [
+    {
+      "fileMatch": ["\\.yml$"],
+      "datasourceTemplate": "custom.hashicorp",
+      "matchStrings": [
+        "#\\s*renovate:\\s*(datasource=(?<datasource>.*?) )?depName=(?<depName>.*?)( versioning=(?<versioning>.*?))?\\s*\\w*:\\s*(?<currentValue>.*)\\s"
+      ],
+      "versioningTemplate": "{{#if versioning}}{{{versioning}}}{{else}}semver{{/if}}"
+    }
+  ],
+  "customDatasources": {
+    "hashicorp": {
+      "defaultRegistryUrlTemplate": "https://api.releases.hashicorp.com/v1/releases/{{packageName}}?license_class=oss",
+      "transformTemplates": [
+        "{ \"releases\": $map($, function($v) { { \"version\": $v.version, \"releaseTimestamp\": $v.timestamp_created, \"changelogUrl\": $v.url_changelog, \"sourceUrl\": $v.url_source_repository } }), \"homepage\": $[0].url_project_website, \"sourceUrl\": $[0].url_source_repository }"
+      ]
+    }
+  },
+}
+```
+
+To have the latest Nomad version in your Ansible variables, use this snippet _after_ adding the above configuration:
+
+```yaml
+# renovate: depName=nomad
+nomad_version: 1.6.0
+```
+
+### Custom offline dependencies
+
+Sometimes the "dependency version source" is _not_ available via an API.
+To work around a missing API, you can create dependency "files". These files are served via HTTP(S), so that Renovate can access them.
+For example, imagine the following file `versiontracker.json` for the software `something``:
+
+```json5
+[
+    {
+        "version": "77"
+    },
+    {
+        "version": "76"
+    },
+]
+```
+
+By writing a custom datasource, Renovate can process the `versiontracker.json` file, see below.
+This example uses Nexus as the webserver.
+
+```json5
+{
+  "customDatasources": {
+    "nexus_generic": {
+      "defaultRegistryUrlTemplate": "https://nexus.example.com/repository/versiontrackers/{{packageName}}/versiontracker.json",
+      "transformTemplates": [
+        "{ \"releases\": $map($, function($v) { { \"version\": $v.version, \"sourceUrl\": $v.filelink } }) }"
+      ]
+    }
+  },
+}
+```
+
+This could be used to update Ansible YAML files with the latest version through a regex manager.
+For example, with the following Ansible content:
+
+```yaml
+# renovate: datasource=custom.nexus_generic depName=something versioning=loose
+something_version: "77"
+```
+
+And the following regex manager:
+
+```json5
+{
+  "regexManagers": [
+    {
+      "fileMatch": ["\\.yml$"],
+      "datasourceTemplate": "custom.nexus_generic",
+      "matchStrings": [
+        "#\\s*renovate:\\s*(datasource=(?<datasource>.*?) )?depName=(?<depName>.*?)( versioning=(?<versioning>.*?))?\\s*\\w*:\\s*\"?(?<currentValue>.+?)\"?\\s"
+      ],
+      "versioningTemplate": "{{#if versioning}}{{{versioning}}}{{else}}semver{{/if}}"
+    }
+  ],
+}
+```