Re-code the commit range action

.github/actions/commit-range/action.yml

@@ -1,43 +1,87 @@
 ---
-# Copyright (c) 2022, Eindhoven University of Technology - CST Robotics Group
-# BDS 3-Clause License (see ./LICENSE.md)
-
-name: 'Commit range'
-description: 'Determine commit range'
+name: 'Get Commit Range'
+description: 'Outputs the commit range for a push or pull request'
 outputs:
-  commit-range:
-    description: 'Range of commits in this run'
-    value: ${{ steps.commit-range.outputs.commit-range }}
+  commit_range:
+    description: 'The commit range'
+    value: ${{ steps.get-range.outputs.range }}
 runs:
   using: "composite"
   steps:
-    - name: Commit range
-      id: commit-range
+    - name: Get commit range
+      id: get-range
+      shell: bash
       env:
-        # Doing this inside run doesn't work because of piping:
-        commit_list: ${{ toJson(github.event.commits) }}
+        GH_TOKEN: ${{ github.token }}
       run: |
-        if [ "${GITHUB_EVENT_NAME}" == "push" ]
-        then
-          NUMBER_COMMITS=$(echo "${commit_list}" | jq 'length')
-          if [ ${NUMBER_COMMITS} -le 1 ]
-          then
-            COMMIT_RANGE=""
+        echo "==== Get Commit Range action ===="
+        echo "Event type: ${{ github.event_name }}"
+
+        if [[ "${{ github.event_name }}" == "pull_request" ]]; then
+          echo "Processing a pull request event"
+          echo "Pull Request number: ${{ github.event.pull_request.number }}"
+          base_sha=${{ github.event.pull_request.base.sha }}
+          head_sha=${{ github.event.pull_request.head.sha }}
+          echo "Base SHA: ${base_sha}"
+          echo "Head SHA: ${head_sha}"
+
+          echo "Fetching merge base from GitHub API..."
+          merge_base=$(gh api \
+            repos/${{ github.repository }}/compare/$base_sha...$head_sha \
+            --jq '.merge_base_commit.sha')
+          echo "Merge base: ${merge_base}"
+
+          range="${merge_base}...${head_sha}"
+          echo "Calculated range: ${range}"
+          echo "range=${range}" >> $GITHUB_OUTPUT
+
+          echo "Explanation: This range represents all commits in the pull request"
+          echo "branch that are not in the base branch, starting from the common"
+          echo "ancestor (merge base)."
+
+        elif [[ "${{ github.event_name }}" == "push" ]]; then
+          echo "Processing a push event"
+          echo "Ref: ${{ github.ref }}"
+          echo "After SHA: ${{ github.sha }}"
+
+          echo "Fetching the pull request information..."
+          pr_info=$(\
+            gh pr list \
+              --head ${{ github.ref_name }} \
+              --json number,baseRefName \
+              --limit 1)
+          if [[ \
+              -n "$pr_info" && \
+              "$(echo "$pr_info" | jq '.[0].baseRefName')" != "null" \
+          ]]; then
+            base_branch=$(echo "$pr_info" | jq -r '.[0].baseRefName')
+            echo "Associated PR found. Base branch: ${base_branch}"
           else
-            OLDEST=$(echo "${commit_list}" | jq 'first.id' | tr -d '"')
-            NEWEST=$(echo "${commit_list}" | jq 'last.id' | tr -d '"')
-            OLDEST_PARENTS=($(git show --no-patch --format="%P" ${OLDEST}))
-            NUMBER_OLDEST_PARENTS=${#OLDEST_PARENTS[@]}
-            # Take second parent if possible,
-            # see https://stackoverflow.com/a/2222920:
-            COMMIT_RANGE="${OLDEST}^${NUMBER_OLDEST_PARENTS}...${NEWEST}"
+            echo "No associated PR found or base branch is null."
+            echo "Using default branch as base."
+            base_branch=$(gh api repos/${{ github.repository }} --jq '.default_branch')
+            echo "Default branch: ${base_branch}"
           fi
-        elif [ "${GITHUB_EVENT_NAME}" == "pull_request" ]
-        then
-          OLDEST=${{ github.event.pull_request.base.sha }}
-          NEWEST=${{ github.event.pull_request.head.sha }}
-          COMMIT_RANGE="${OLDEST}...${NEWEST}"
+
+          echo "Fetching the branch point..."
+          if ! branch_point=$(git merge-base origin/${base_branch} ${{ github.sha }})
+          then
+            echo "Failed to find merge-base."
+            echo "Using the first commit of the current branch."
+            branch_point=$(git rev-list --max-parents=0 HEAD)
+          fi
+          echo "Branch point: ${branch_point}"
+
+          range="${branch_point}...${{ github.sha }}"
+          echo "Calculated range: ${range}"
+          echo "range=${range}" >> $GITHUB_OUTPUT
+
+          echo "This range represents all commits in ${{ github.ref }} since it"
+          echo "diverged from ${base_branch}."
+
+        else
+          echo "Error: Unsupported event type: ${{ github.event_name }}"
+          exit 1
         fi
-        echo -e "\e[35m\e[1m COMMIT_RANGE = ${COMMIT_RANGE} \e[0m"
-        echo "commit-range=${COMMIT_RANGE}" >> $GITHUB_OUTPUT
-      shell: bash
+
+        echo "==== Get Commit Range action complete ===="