NEW Create action

.github/workflows/auto-tag.yml

@@ -0,0 +1,12 @@
+name: Auto-tag
+on:
+  push:
+    tags:
+      - '*.*.*'
+jobs:
+  auto-tag:
+    name: Auto-tag
+    runs-on: ubuntu-latest
+    steps:
+      - name: Auto-tag
+        uses: silverstripe/gha-auto-tag@main

README.md

@@ -1 +1,32 @@
-# gha-auto-tag
+# GitHub Actions - Auto-tag
+
+Delete and re-release tags so that other modules can use something similar to carets (^)
+
+Caret (^) requirements are not supported by github-action e.g. @^2 does not work
+
+The action will tag v2 when 2.5.0 is released and v0.3 when 0.3.5 is released
+
+The new 'v' tag will point to the same sha  e.g. the sha of v2 will equal the sha of 2.5.0
+
+This allows modules to include workflows using the @v2 or @v0.3 syntax
+
+Using the 'v' prefix to avoid confusion with the '2' branch naming convention that Silverstripe uses
+
+## Usage
+
+This action has no configuration or inputs - just add the following workflow verbatim.
+
+**.github/workflows/auto-tag.yml**
+```yml
+on:
+  push:
+    tags:
+      - '*.*.*'
+jobs:
+  auto-tag:
+    name: Auto-tag
+    runs-on: ubuntu-latest
+    steps:
+      - name: Auto-tag
+        uses: silverstripe/gha-auto-tag@main
+```

action.yml

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+name: Auto-tag
+description: Automatically delete and re-release tags so that other github action modules can use something similar to carets e.g. v0.1 or v3
+
+runs:
+  using: composite
+  steps:
+
+    - name: Generate tag name
+      id: generate_tag_name
+      shell: bash
+      env:
+        GITHUB_REF: ${{ github.ref }}
+      run: |
+        # refs/tags/0.1.23 => 0.1.23
+        TAG=$(echo $GITHUB_REF | cut -c 11-)
+        if ! [[ $TAG =~ ^([0-9]+)\.([0-9]+)\.([0-9]+)$ ]]; then
+          echo "Invalid semver tag $TAG"
+          exit 1
+        fi 
+        MAJOR="${BASH_REMATCH[1]}"
+        MINOR="${BASH_REMATCH[2]}"
+        PATCH="${BASH_REMATCH[3]}"
+        NEW_TAG="v${MAJOR}"
+        if [ "$MAJOR" == "0" ]; then
+          NEW_TAG=("v${MAJOR}.${MINOR}")
+        fi
+        echo "Tag is $NEW_TAG"
+        echo "::set-output name=tag::$NEW_TAG"
+
+    - name: Add tag to repo
+      uses: silverstripe/gha-tag-release@main
+      with:
+        tag: ${{ steps.generate_tag_name.outputs.tag }}
+        delete_existing: true
+        release: false