Document (revise?) how dependencies from file sources are combined

[riccardoporreca]

When processing file sources, it looks like only the last specification of a conda package version (by package name) is preserved

e.g.

# environment-foo.yml
channels:
- conda-forge
dependencies:
- python=3.8.12
- numpy=1.22.3

# environment-bar.yml
channels:
- conda-forge
dependencies:
- python=3.8.12
- numpy=1.22.2

conda-lock -f environment-foo.yml -f environment-bar.yml -p linux-64
INFO:conda_lock.conda_solver:linux-64 using specs ['python 3.8.12.*', 'numpy 1.22.2.*']

conda-lock -f environment-bar.yml -f environment-foo.yml -p linux-64
INFO:conda_lock.conda_solver:linux-64 using specs ['python 3.8.12.*', 'numpy 1.22.3.*']

Is this by design? Would it be possible to resolve to the union of the specified dependencies?
The behavior, if unchanged, should be best documented in Compound specification

The relevant code seems to be

https://github.com/conda-incubator/conda-lock/blob/42923b3bd280a260f1480d45a5c7104546e44580/conda_lock/src_parser/__init__.py#L336-L346

(As a side note, it looks lines 341-342 are not effective given line 344)

[mariusvniekerk]

@riccardoporreca This is by design. Files specified later are intended to be overrides to the specifications earlier

[riccardoporreca]

Thanks for clarifying this @mariusvniekerk, happy to draft a documentation PR if you agree.