SiteAliasName

Parse a string that contains a site alias name, and provide convenience methods to access the parts.

When provided by users, aliases must be in one of the following forms:

• @sitename.env: List only sitename and environment.

• @env: Look up a named environment in instances where the site root is known (e.g. via cwd). In this form, there is an implicit sitename 'self' which is replaced by the actual site alias name once known.

• @sitename: Provides only the sitename; uses the 'default' environment, or 'dev' if there is no 'default' (or whatever is there if there is only one). With this form, the site alias name has no environment until the appropriate default environment is looked up. This form is checked only after @env returns no matches.

There are also two special aliases that are recognized:

• @self: The current bootstrapped site.

• @none: No alias ('root' and 'uri' unset).

The special alias forms have no environment component.

When provided to an API, the '@' is optional.

Note that @sitename and @env are ambiguous. Aliases in this form (that are not one of the special aliases) will first be assumed to be @env, and may be converted to @sitename later.

Note that:

• 'sitename' and 'env' MUST NOT contain a '.' (unlike previous versions of Drush).
• Users SHOULD NOT create any environments that have the same name as any site name (and visa-versa).
• All environments in one site record SHOULD be different versions of the same site (e.g. dev / test / live).