Global defaults for some keywords

[x80486]

Clear and concise description of the problem

Woodpecker CI could benefit from using some defaults to avoid repetitive blocks and/or references to anchors.

This is something I used to use in GitLab CI and it makes the pipeline really compact. For instance, they have a default keyword to configure some "default" values that apply to all subsequent steps — when relevant.

Suggested solution

default:
  image: docker.io/library/rust:1.61-slim-bullseye

pipeline:
  format:
    commands:
      - rustup component add rustfmt
      - cargo fmt -- --check
    environment:
      CARGO_HOME: .cargo/
    group: verify
    # No need to specify image here since it's inferred by "default"
  assemble:
    commands:
      - cargo build
    environment:
      CARGO_HOME: .cargo/
    group: assemble
    # No need to specify image here since it's inferred by "default"
  publish:
    commands:
      - cargo blah
    environment:
      CARGO_HOME: .cargo/
    group: publish
    image: docker.io/library/rust:1.62-slim-bullseye # ...if defined, overwrites what's in default

Alternative

YAML aliases and anchors 😒

Additional context

No response

Validations

• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.