Support conversion of .conda format with conda convert

[atteggiani]

Checklist

• I added a descriptive title
• I searched open requests and couldn't find a duplicate

Overview

When trying to convert a .conda package using conda convert, I got an error similar to the following:

File "/Users/username/anaconda3/lib/python3.9/site-packages/conda_build/api.py", line 382, in convert
    raise RuntimeError("cannot convert: %s" % package_file)
RuntimeError: cannot convert: name_of_package.conda

This is also clear by looking around line 382 of the api.py source code that raised the issue:

conda-build/conda_build/api.py

Lines 365 to 382 in e5b060e

	if package_file.endswith("tar.bz2"):
	return conda_convert(
	package_file,
	output_dir=output_dir,
	show_imports=show_imports,
	platforms=platforms,
	force=force,
	verbose=verbose,
	quiet=quiet,
	dry_run=dry_run,
	dependencies=dependencies,
	)
	elif package_file.endswith(".whl"):
	raise RuntimeError(
	"Conversion from wheel packages is not implemented yet, stay tuned."
	)
	else:
	raise RuntimeError(f"cannot convert: {package_file}")

There is no mention to .conda format.

Steps to reproduce the error

The error can be reproduced with any attempt to convert a .conda format built package using:

conda convert name_of_package.conda ...

Why is this needed?

Since conda-build 25.1.0 .conda is the new default package format.

Therefore, I think it would be useful to be able to use conda convert directly on a .conda format package.

What should happen?

The command:

conda convert package_name.conda ...

should successfully convert a .conda format package, as it does for the tar.bz2 format.