Add readme

tools/amplify-preview/README.md

@@ -0,0 +1,94 @@
+# amplify-preview
+
+
+This gha-tool is basically re-implements what [AWS Amplify's GitHub integration should be doing](https://docs.aws.amazon.com/amplify/latest/userguide/pr-previews.html),
+however because of following limitations, we can't really use it for some of the repos:
+- [No way to filter for which PRs to generate preview deployments](https://github.com/aws-amplify/amplify-hosting/issues/3960)
+- [Hard limit of 50 preview branches per amplify app][https://docs.aws.amazon.com/amplify/latest/userguide/quotas-chapter.html]
+- [No way to create PR preview programmatically](https://github.com/aws-amplify/amplify-hosting/issues/3963)
+
+This action accepts of AWS Amplify App IDs, checks if current git branch is connected to the apps and posts deployment status and PR preview in PR comments.
+
+If `--create-branches` is enabled, then it will also connect git branch to one of the AWS Amplify apps (where hard limit of 50 branches hasn't been reached yet) and kick of new build.
+If `--wait` is enabled, then it will also wait for deployment to be completed and fail the GHA run if deployment had failed.
+
+## Usage
+
+```shell
+usage: amplify-preview --amplify-app-ids=AMPLIFY-APP-IDS --git-branch-name=GIT-BRANCH-NAME [<flags>]
+
+Flags:
+  --[no-]help            Show context-sensitive help (also try --help-long and --help-man).
+  --amplify-app-ids=AMPLIFY-APP-IDS ...  
+                         List of Amplify App IDs ($AMPLIFY_APP_IDS)
+  --git-branch-name=GIT-BRANCH-NAME  
+                         Git branch name ($GIT_BRANCH_NAME)
+  --[no-]create-branches  Defines whether Amplify branches should be created if missing, or just lookup existing ones ($CREATE_BRANCHES)
+  --[no-]wait            Wait for pending/running job to complete ($WAIT)
+```
+
+Example GHA workflow:
+
+```yaml
+name: Amplify Preview
+on:
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  # Permissions to write PR comment
+  pull-requests: write
+  id-token: write
+
+jobs:
+  amplify-preview:
+    name: Get and post Amplify preview URL
+    runs-on: ubuntu-22.04-2core-arm64
+    environment: docs-amplify
+    steps:
+    - name: Checkout shared-workflow
+      uses: actions/checkout@v4
+      with:
+        repository: gravitational/shared-workflows
+        sparse-checkout: |
+          tools
+
+    - name: Configure AWS credentials
+      uses: aws-actions/configure-aws-credentials@e3dd6a429d7300a6a4c196c26e071d42e0343502 # v4
+      with:
+        aws-region: us-west-2
+        role-to-assume: ${{ vars.IAM_ROLE }}
+
+    - name: Check Amplify job status test
+      uses: ./tools/amplify-preview
+      with:
+        app_ids: ${{ vars.AMPLIFY_APP_IDS }}
+        create_branches: "true"
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+        wait: "true"
+```
+
+## AWS Permissions
+
+For this action to work, AWS role with following IAM permissions is required:
+```json
+{
+    "Statement": [
+        {
+            "Action": [
+                "amplify:CreateBranch",
+                "amplify:GetBranch",
+                "amplify:ListJobs"
+                "amplify:StartJob",
+            ],
+            "Effect": "Allow",
+            "Resource": [
+                "arn:aws:amplify:<region>:<account_id>:apps/<app_id>/branches/*"
+            ]
+        }
+    ],
+    "Version": "2012-10-17"
+}
+```
+
+Where `amplify:CreateBranch` and `amplify:StartJob` are needed only when `--create-branches` is enabled.

tools/amplify-preview/main.go

@@ -37,7 +37,7 @@ var (
 
 	amplifyAppIDs  = kingpin.Flag("amplify-app-ids", "List of Amplify App IDs").Envar("AMPLIFY_APP_IDS").Required().Strings()
 	gitBranchName  = kingpin.Flag("git-branch-name", "Git branch name").Envar("GIT_BRANCH_NAME").Required().String()
-	createBranches = kingpin.Flag("crate-branches",
+	createBranches = kingpin.Flag("create-branches",
 		"Defines whether Amplify branches should be created if missing, or just lookup existing ones").Envar("CREATE_BRANCHES").Default("false").Bool()
 	wait = kingpin.Flag("wait",
 		"Wait for pending/running job to complete").Envar("WAIT").Default("false").Bool()