@callback accepts_options(app :: atom(), opts()) :: opts() | nil

This behaviour function receives a keyword list of opts and should return an updated list in case the SCM consumes the available options. For example, when a developer specifies a dependency:

{:foo, "0.1.0", github: "foo/bar"}

Each registered SCM will be asked if they consume this dependency, receiving [github: "foo/bar"] as argument. Since this option makes sense for the Git SCM, it will return an update list of options while other SCMs would simply return nil.

@callback checked_out?(opts()) :: boolean()

This behaviour function returns a boolean if the dependency is available.

@callback checkout(opts()) :: any()

This behaviour function checks out dependencies.

If the dependency is locked, a lock is received in opts and the repository must be check out at the lock. Otherwise, no lock is given and the repository can be checked out to the latest version.

It must return the current lock.

@callback equal?(opts1 :: opts(), opts2 :: opts()) :: boolean()

Receives two options and must return true if they refer to the same repository. The options are guaranteed to belong to the same SCM.

@callback fetchable?() :: boolean()

Returns a boolean if the dependency can be fetched or it is meant to be previously available in the file system.

Local dependencies (i.e. non-fetchable ones) are automatically recompiled every time the parent project is compiled.

@callback format(opts()) :: String.t()

Returns a string representing the SCM. This is used when printing the dependency and not for inspection, so the amount of information should be concise and easy to spot.

@callback format_lock(opts()) :: String.t() | nil

Returns a string representing the SCM. This is used when printing the dependency and not for inspection, so the amount of information should be concise and easy to spot.

If nil is returned, it means no lock information is available.

@callback lock_status(opts()) :: :mismatch | :outdated | :ok

This behaviour function checks the status of the lock. In particular, it checks if the revision stored in the lock is the same as the repository it is currently in.

It may return:

• :mismatch - if the lock doesn't match and we need to simply move to the latest lock

• :outdated - the repository options are outdated in the lock and we need to trigger a full update

• :ok - everything is fine

The lock is sent via opts[:lock] but it may not always be available. In such cases, if the SCM requires a lock, it must return :mismatch, otherwise simply :ok.

Note the lock may also belong to another SCM and as such, an structural check is required. A structural mismatch should always return :outdated.

@callback managers(opts()) :: [atom()]

Returns the usable managers for the dependency. This can be used if the SCM has extra knowledge of the dependency, otherwise it should return an empty list.

@callback update(opts()) :: any()

This behaviour function updates dependencies. It may be called by deps.get or deps.update.

In the first scenario, a lock is received in opts and the repository must be updated to the lock. In the second, no lock is given and the repository can be updated freely.

It must return the current lock.