Refactor Flux GitHub Action

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

action/action.yml

@@ -1,15 +1,38 @@
-name: 'kustomize'
-description: 'A GitHub Action for running Flux commands'
-author: 'Flux project'
+name: Setup Flux CLI
+description: A GitHub Action for running Flux commands
+author: Stefan Prodan
 branding:
-  icon: 'command'
-  color: 'blue'
+  color: blue
+  icon: command
 inputs:
   version:
-    description: 'strict semver'
+    description: "Flux version e.g. 0.8.0 (defaults to latest stable release)"
     required: false
 runs:
-  using: 'docker'
-  image: 'Dockerfile'
-  args:
-    - ${{ inputs.version }}
+  using: composite
+  steps:
+    - name: "Download flux binary to tmp"
+      shell: bash
+      run: |
+        VERSION=${{ inputs.version }}
+
+        if [ -z $VERSION ]; then
+          VERSION=$(curl https://api.github.com/repos/fluxcd/flux2/releases/latest -sL | grep tag_name | sed -E 's/.*"([^"]+)".*/\1/' | cut -c 2-)
+        fi
+
+        BIN_URL="https://github.com/fluxcd/flux2/releases/download/v${VERSION}/flux_${VERSION}_linux_amd64.tar.gz"
+        curl -sL ${BIN_URL} -o /tmp/flux.tar.gz
+        mkdir -p /tmp/flux
+        tar -C /tmp/flux/ -zxvf /tmp/flux.tar.gz
+    - name: "Add flux binary to /usr/local/bin"
+      shell: bash
+      run: |
+        sudo cp /tmp/flux/flux /usr/local/bin
+    - name: "Cleanup tmp"
+      shell: bash
+      run: |
+        rm -rf /tmp/flux/ /tmp/flux.tar.gz
+    - name: "Verify correct installation of binary"
+      shell: bash
+      run: |
+        flux -v