Improve robustness of GDIT Action (#56)

* Add test workflow for invoking GDIT Action

* Modularize the GDIT Action

* Remove extra `if` from Action step

* Expand displayed arrays using `[@]`

* Add missing `{}` to displayed arrays

* Replace arrays with strings

* Fix names of step outputs

* Mock Story tags output

* Remove  `,` prefix from Story tags

* Use GitHub API to determine PR number

* Add `GITHUB_TOKEN` input variable

* Try uncommenting API call to Shortcut

* Try using `github.token` in action

* Add debug information

* Derive better SHA

* Fix indentation of SHA step

* Add names to steps

* Remove mock Shortcut API token

* Add PR number requirement to Shortcut Stories step

* Temporarily add back mock Shortcut API token to test error

* Remove mock Shortcut API token

* Remove test workflow

generate-docker-image-tags/action.yml

@@ -15,24 +15,27 @@ description: Generate a list of Docker image tags for the current workflow.
 
 inputs:
   shortcut-api-token:
-    description: Shortcut API token for fetching Story IDs related to a PR.
+    description: >
+      Shortcut API token for fetching Story IDs related to a PR.
     required: false
   prefix:
-    description: |
-      The prefix for tagging commits that are not yet merged to main/master.
-      For example: a PR from some-branch would receive the tags <prefix>.some-branch, <prefix>.<COMMIT_SHA>.
+    description: >
+      Prefix for tagging commits that are not yet merged to main/master.
+      For example, a PR from some-branch would receive tags "<prefix>.some-branch"
+      and "<prefix>.<COMMIT_SHA>".
     required: false
     default: temp
 
 outputs:
   tags:
     description: Comma-separated list of tags.
-    value: ${{ steps.get-tags.outputs.tags }}
+    value: ${{ steps.get-all-tags.outputs.tags }}
 
 runs:
   using: composite
   steps:
-    - id: get-branch
+    - name: Get Branch
+      id: get-branch
       shell: bash
       run: |
         if [ "$GITHUB_EVENT_NAME" == "pull_request" ]
@@ -45,55 +48,95 @@ runs:
           printf 'Cannot determine tags: Workflow must be triggered by "push", "pull_request", or "release" event.' && exit 1
         fi
 
+        echo "Branch is '$BRANCH'."
         echo "branch=$BRANCH" >> $GITHUB_OUTPUT
 
-    - id: get-tags
+    - name: Get Commit SHA
+      id: get-sha
       shell: bash
       run: |
-        BRANCH=${{ steps.get-branch.outputs.branch }}
-        COMMIT_SHA=${GITHUB_SHA:0:7}
+        SHA="${{ github.event.pull_request.head.sha || github.sha }}"
+        SHA=${SHA:0:7}
+        echo "SHA is '$SHA'."
+        echo "sha=$SHA" >> $GITHUB_OUTPUT
+
+    - name: Get PR Number
+      id: get-pr-number
+      shell: bash
+      env:
+        GITHUB_TOKEN: ${{ github.token }}
+      run: |
+        SHA="${{ steps.get-sha.outputs.sha }}"
+
+        PR_NUMBER=$(
+          gh api \
+            -H "Accept: application/vnd.github+json" \
+            -H "X-GitHub-Api-Version: 2022-11-28" \
+            /repos/$GITHUB_REPOSITORY/commits/$SHA/pulls \
+            | jq -r ".[].number"
+        )
+
+        echo "PR number is '$PR_NUMBER'."
+        echo "pr-number=$PR_NUMBER" >> $GITHUB_OUTPUT
+
+    - name: Get Tags for Shortcut Stories
+      id: get-story-tags
+      shell: bash
+      if: ${{ inputs.shortcut-api-token && steps.get-pr-number.outputs.pr-number }}
+      run: |
+        PR_NUMBER="${{ steps.get-pr-number.outputs.pr-number }}"
+        url="$GITHUB_SERVER_URL/$GITHUB_REPOSITORY/pull/$PR_NUMBER"
+
+        ids=$(
+          curl --silent -X GET \
+          -H "Content-Type: application/json" \
+          -H "Shortcut-Token: ${{ inputs.shortcut-api-token }}" \
+          -d "{ \"page_size\": 20, \"query\": \"is:story and pr:$url\" }" \
+          -L "https://api.app.shortcut.com/api/v3/search" \
+          | jq ".stories.data[].id"
+        )
+
+        TAGS=""
+        while read -r id; do
+          if [ ! -z "$id" ]; then
+            TAGS+="sc-$id,"
+          fi
+        done <<< "$ids"
+
+        # Remove the trailing comma.
+        TAGS="${TAGS::-1}"
+
+        echo "Story tags are '$TAGS'."
+        echo "tags=$TAGS" >> $GITHUB_OUTPUT
+
+    - name: Get Tags for Branch
+      id: get-branch-tags
+      shell: bash
+      run: |
+        BRANCH="${{ steps.get-branch.outputs.branch }}"
+        SHA="${{ steps.get-sha.outputs.sha }}"
 
         if [ "$BRANCH" == "main" ] || [ "$BRANCH" == "master" ]
         then
-          TAGS="latest,$BRANCH,$COMMIT_SHA"
+          TAGS="latest,$BRANCH,$SHA"
         else
           SLASHLESS_BRANCH=`echo $BRANCH | tr / -`
-          TAGS="${{ inputs.prefix }}.$SLASHLESS_BRANCH,${{ inputs.prefix }}.$COMMIT_SHA"
+          TAGS="${{ inputs.prefix }}.$SLASHLESS_BRANCH,${{ inputs.prefix }}.$SHA"
         fi
 
-        if [ "$GITHUB_EVENT_NAME" == "pull_request" ]
-        then
-          PR_NUMBER="${{ github.event.number }}"
-        elif [ "$GITHUB_EVENT_NAME" == "push" ]
-        then
-          # Workflow was triggered by a "push" event.
-          PR_NUMBER=$( \
-            (echo '${{ github.event.head_commit.message }}' \
-            | grep -o "\(#[0-9]\+\)" || true) \
-            | sed "s/[#()]//g" \
-          )
-        else
-          PR_NUMBER=""
-        fi
+        echo "Branch tags are '$TAGS'."
+        echo "tags=$TAGS" >> $GITHUB_OUTPUT
 
-        # Add additional tags for each Story ID associated with this PR.
-        if [ ! -z "$PR_NUMBER" ] && [ ! -z "${{ inputs.shortcut-api-token }}" ]; then
-          url="$GITHUB_SERVER_URL/$GITHUB_REPOSITORY/pull/$PR_NUMBER"
-
-          ids=$(
-            curl --silent -X GET \
-            -H "Content-Type: application/json" \
-            -H "Shortcut-Token: ${{ inputs.shortcut-api-token }}" \
-            -d "{ \"page_size\": 20, \"query\": \"is:story and pr:$url\" }" \
-            -L "https://api.app.shortcut.com/api/v3/search" \
-            | jq ".stories.data[].id"
-          )
-
-          while read -r id; do
-            if [ ! -z "$id" ]; then
-              TAGS="$TAGS,sc-$id"
-            fi
-          done <<< "$ids"
-        fi
+    - name: Get All Tags
+      id: get-all-tags
+      shell: bash
+      run: |
+        BRANCH_TAGS="${{ steps.get-branch-tags.outputs.tags }}"
+        STORY_TAGS="${{ steps.get-story-tags.outputs.tags }}"
+
+        TAGS="$BRANCH_TAGS,$STORY_TAGS"
+        TAGS="${TAGS/%,/}"
+        TAGS="${TAGS/#,/}"
 
+        echo "Tags are '$TAGS'."
         echo "tags=$TAGS" >> $GITHUB_OUTPUT