[RFC] Dependencies in user rule outside the workspace.

[bobot]

Expected Behavior

• Don't raise an exception ;) already the case
• Support it? by being like external path.

Actual Behavior

Using a path outside the workspace is not well supported nor checked:

• using %{dep:/home/user/foo.txt} raise an exception when translating it to internal path (failed only for <= 2.7)
• using %{dep:../foo.txt} in a dune file at the root of the workspace is accepted even if it corresponds to _build/foo.txt.
• using %{dep:../../foo.txt} in a dune file at the root of the workspace is refused with a nice message.

Reproduction

Tests in #4035

Additional information

I would have wanted to support such user dependencies (backtracking/mlpost#14), as we do for absolute path:

• we can support the relative path in rule dependencies.
• and support it in copy_files stanza.

(EDIT: absolute path works in dev)

[bobot]

Meeting:

• Ok: consider them as absolute external path