Adding recipes to foreign Justfiles (fallback without fallback)

[jirijakes]

I would like to add my own recipes to projects within a directory. Normally, a parent Justfile and set fallback would do the job but these Justfiles do not have this setting (they come with external projects).

For example, when in projects/a/, I would like to call a recipe. If the recipe is not found in projects/a/Justfile, it would be searched in projects/Justfile. Exactly like fallback.

└── projects
    ├── a
    │   └── Justfile (shipped with project a)
    ├── b
    │   └── Justfile (shipped with project b)
    └── Justfile (my own)

Does somebody have an idea? Perhaps my problem boils down to: is there a way how to force a setting onto a foreign Justfile?

just --set fallback does not work due to: Variable 'fallback' overridden on the command line but not present in justfile. I know about just ../recipe; it works but is not ideal, I have to know in which Justfile the recipe is.

Also, projects a/ and b/ are pretty unstable – they are git repositories, new projects come and go, there are frequent worktrees, pulls etc., so modifying the project Justfiles would be pretty inconvenient.