GH-200

Debug messages are written with the debug workflow command, ::debug::{message}, for example echo "::debug::Set variable myVariable to true". They appear in the log only when step debug logging is enabled (ACTIONS_STEP_DEBUG set to true). There is no DEBUG_MESSAGE environment file, ::add-mask:: hides a value in the logs instead of printing it, and writing to GITHUB_OUTPUT sets a step output rather than logging a message.

Workflow commands are how actions and run steps communicate with the runner machine to set environment variables, set output values used by other actions, add debug messages to the logs and perform similar tasks. Enabling debug logging only makes extra log output visible, environment variables are just values, and composite steps and self-hosted runners do not provide a channel to the runner.

GITHUB_TOKEN is an installation access token created for each job, used to authenticate on behalf of GitHub Actions, for example when calling the GitHub API for the workflow's repository. It is not an SSH credential, secrets are read through the secrets context without it, and public Marketplace actions are referenced with uses: without any token.

A job on a GitHub-hosted runner can run for at most 6 hours, while a job on a self-hosted runner can run for up to 5 days. A self-hosted runner also sits on your own network, so it can reach and install software from local network resources that GitHub-hosted runners cannot. Self-hosted runners do not consume GitHub Actions minutes, and macOS runners are available as GitHub-hosted runners.

A Redis service container is created fresh for the job and destroyed when the job completes, so nothing is left behind on the self-hosted runner for future runs; self-hosted runners only need to be Linux machines with Docker installed. Installing Redis on the runner image or with a run step changes the persistent runner state, and a separate shared Redis machine keeps data between runs.

Add a custom label such as custom-software to the runner, then have users target it in runs-on with the labels custom-software and linux. The linux label is one of the default labels the runner receives automatically, so it does not need to be added. Runner groups control access rather than identifying installed software, and no webhook setup is needed because the runner polls GitHub for jobs.

The repository_dispatch event is triggered through the GitHub API, with a custom event_type, when you want to run a workflow for activity that happens outside of GitHub. workflow_run fires when another workflow is requested or completes, deployment fires when a deployment is created, and check_suite fires on check suite activity inside GitHub.

A workflow can use actions from the same repository as the workflow file, from any public repository (owner/repo@ref), and from a published Docker container image on Docker Hub (docker://image:tag). Actions are not pulled from an NPM registry, there is no .action file type, runs-on selects the runner rather than an action, and the Secrets settings page stores secrets, not actions.

GitHub documents that scheduled workflows run on the latest commit on the default branch, and that they only run on the default branch. A schedule has no triggering branch, so the latest commit on the branch that triggered the run does not apply. The default branch need not be named main, and there is no special branch named schedule. The workflow file also cannot pin a commit for a schedule.

The env key can be set for the entire workflow at the top level, for a job with jobs.<job_id>.env, and for a single step with jobs.<job_id>.steps[*].env. The more specific level overrides the broader one. The defaults key sets default shell and working directory, not environment variables. Workflow syntax has no runner or stage level for env.

github.ref_name is the short name of the branch or tag that triggered the run, for example feature-branch, so comparing it in the job-level if condition works. github.ref is a string such as refs/heads/feature-branch, so it has no name property. The github context has no branch or branch_name property, so options B and D are not valid.

To publish to GitHub Marketplace, the repository must contain a single action metadata file (action.yml or action.yaml) at its root. The action's name cannot match a GitHub user or organization unless that owner is publishing it. The action must be in a public repository, so A is wrong. The name must not match an existing Marketplace category, which is the opposite of D. A repository can hold only one action, so E is wrong.

Custom environment variables are set with the env key as a YAML map, for example env: followed by MY_VARIABLE: my-value. The equals-sign forms are not valid YAML mappings. The environment key selects a deployment environment, not variables, and var is not a workflow key at all.

The workflow_run event lets a workflow run when another workflow is requested or completed. You can filter it on the build workflow's name and check its conclusion for success, all without changing the build workflow. repository_dispatch requires something to send an API call, which means changing the build workflow. workflow_dispatch is a manual trigger, and workflow_exec does not exist.

A step defines environment variables with the env key as a map of names to values, and the run command then reads it as $dbserver. Workflow steps have no variables key. A list of name and value pairs is Kubernetes or Azure Pipelines style, not GitHub Actions syntax. environment is a job-level key for deployment environments.

GITHUB_TOKEN is a repository-scoped installation token. With packages: write it can publish to GitHub Packages, and with issues: write it can create issues through the API. It cannot manage secrets or organization membership, because those need a personal access token or a GitHub App. Reading the runner's file system and using a self-hosted runner need no token at all.

The run keyword executes command-line programs, and the literal block indicator (|) lets a single step run several commands, one per line, so npm ci and npm run build both run. The shell keyword only selects the shell that runs the commands, so a step with shell and no run executes nothing. nodejs is not a supported shell value (bash, pwsh, python, sh, cmd and powershell are), so the snippet that sets shell: nodejs fails. Without the |, the YAML folds the lines into a single command, npm ci npm run build, instead of running two commands.

Environment variables can be set in the workflow env mapping, in a job, or in a single step (jobs.<job_id>.steps[*].env). A variable defined in a step exists only for that step and overrides job-level and workflow-level variables with the same name, which makes the step the smallest scope. A job-level variable applies to every step in the job, and the workflow env mapping applies to all jobs.

The workflow_dispatch event lets you start a workflow manually from the Actions tab, with GitHub CLI or through the REST API, and it can define inputs. workflow_run fires automatically when another workflow is requested or completes. status fires when a commit status changes, and create fires when a branch or tag is created, so neither of them is a manual trigger.

Workflows are YAML files that must be stored in the .github/workflows directory of the repository, and GitHub only runs workflow files from that directory when their events occur. They are not attached to actions through the user interface. .workflows/ is not a recognized location, and .github/actions/ is a common place for local custom actions, not for workflows.