feat: add cancel-redundant-workflows command (#28)

src/commands/cancel-redundant-workflows.yml

@@ -0,0 +1,12 @@
+description: >
+  Cancels any previous running or on-hold workflows for the same branch.
+
+  CircleCI can do this automatically when this feature is enabled in project settings for all branches EXCEPT the default branch.
+  There is however no way to filter what branches are affected or to include the default branch.
+  This command can be used with an appropriate `when` step to do this.
+
+  This command requires a CIRCLE_TOKEN env var to be set with a valid CircleCi API Token.
+steps:
+  - run:
+      name: Cancelling redundant workflows
+      command: << include(scripts/cancel-redundant-workflows.sh) >>

src/scripts/cancel-redundant-workflows.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+
+if [ -z "$BASH" ]; then
+  echo "Bash not installed. Aborting."
+  exit 1
+fi
+hash curl 2>/dev/null || { echo >&2 "curl is not installed. Aborting."; exit 1; }
+if [ -z "$CIRCLE_TOKEN" ]; then
+  echo "CIRCLE_TOKEN env not set. Please set a valid CircleCi API Token in the env var CIRCLE_TOKEN";
+  exit 1;
+fi
+
+# Get the name of the workflow and the related pipeline number
+CURRENT_WORKFLOW_URL="https://circleci.com/api/v2/workflow/${CIRCLE_WORKFLOW_ID}?circle-token=$CIRCLE_TOKEN"
+curl -f -s --retry 3 --retry-all-errors "$CURRENT_WORKFLOW_URL" > /tmp/aks/current_wf.json
+WORKFLOW_NAME="$(jq -r '.name' /tmp/aks/current_wf.json)"
+CURRENT_PIPELINE_NUM="$(jq -r '.pipeline_number' /tmp/aks/current_wf.json)"
+
+# Get the IDs of pipelines created for the same branch. (Only consider pipelines that have a pipeline number smaller than the current pipeline)
+PIPELINES_URL="https://circleci.com/api/v2/project/gh/$CIRCLE_PROJECT_USERNAME/$CIRCLE_PROJECT_REPONAME/pipeline?circle-token=$CIRCLE_TOKEN&branch=$CIRCLE_BRANCH"
+curl -f -s --retry 3 --retry-all-errors "$PIPELINES_URL" >> /tmp/aks/pipelines.json
+PIPELINE_IDS=$(jq -r --argjson CURRENT_PIPELINE_NUM "$CURRENT_PIPELINE_NUM" '.items[]|select(.state == "created")|select(.number < $CURRENT_PIPELINE_NUM)|.id | values')
+
+## Get the IDs of currently running/on_hold workflows that have the same name as the current workflow, in all previously created pipelines.
+if [ -n "$PIPELINE_IDS" ]; then
+  for PIPELINE_ID in $PIPELINE_IDS
+  do
+    curl -f -s --retry 3 --retry-all-errors "https://circleci.com/api/v2/pipeline/${PIPELINE_ID}/workflow?circle-token=$CIRCLE_TOKEN" | jq -r --arg workflow_name "${WORKFLOW_NAME}" '.items[] | select(.status == "on_hold" or .status == "running") | select(.name == $workflow_name) | .id | values' >> /tmp/aks/wf_to_cancel
+  done
+fi
+
+## Cancel any currently running/on_hold workflow with the same name
+if [ -s /tmp/aks/wf_to_cancel ]; then
+  echo "Cancelling the following redundant workflow(s):"
+  cat /tmp/aks/wf_to_cancel
+  while read -r WORKFLOW_ID;
+    do
+      curl -f -s --retry 3 --retry-all-errors --header "Circle-Token: $CIRCLE_TOKEN" --request POST "https://circleci.com/api/v2/workflow/$WORKFLOW_ID/cancel"
+    done < /tmp/aks/wf_to_cancel
+  else
+    echo "Nothing to cancel"
+fi