message: Document `workspace.default-members`
diff: @@ -520,8 +520,19 @@ crate will be treated as a normal package, as well as a workspace. If the
  manifest*.
  When working with *virtual manifests*, package-related cargo commands, like
  -`cargo build`, default to all packages in the workspace as if `--all` was used.
  -This can be changed by passing a `--package` or `-p` command-line parameters.
  +`cargo build`, default to the set of packages specified by the `default-members`
  +configuration:
  +
  +```toml
  +[workspace]
  +members = ["path/to/member1", "path/to/member2", "path/to/member3/*"]
  +
  +# The members that commands like `cargo build` apply to by deault.
  +# This must expand to a subset of `members`.
  +# Optional key, defaults to the same as `members`
  +# (as if `--all` were used on the command line).
  +default-members = ["path/to/member2", "path/to/member3/*"]
  +```
  # The project layout
  