Fix logic for running without --file sources #231
Description
Running w/o sources for dependencies is allowed by design (and would use the sources from the lockfile).
However, the CLI interface checks the existence of an environment.y(a)ml file for such cases, as this is the default:
How to reproduce
# environment-foo.yml
channels:
- conda-forge
dependencies:
- python=3.8.12
- numpy=1.22.3
platforms:
- win-64conda-lock -f environment-foo.yml --lockfile conda-lock.yml
# Locking dependencies for ['win-64']...
# INFO:conda_lock.conda_solver:win-64 using specs ['python 3.8.12.*', 'numpy 1.22.3.*']Running with lock-file only shows the help because no environment.y(a)ml exists:
conda-lock --lockfile conda-lock.yml
# Usage: conda-lock lock [OPTIONS]
# [...]If we just create an empty environment.yml, the CLI gets past the check above and the rest behaves as expected
conda-lock --lockfile conda-lock.yml
# Locking dependencies for ['win-64']...
# INFO:conda_lock.conda_solver:win-64 using specs ['python 3.8.12.*', 'numpy 1.22.3.*']