Documentation: Add Description of package_spec (or reference to)

[phreed]

Checklist

• I added a descriptive title
• I searched for other issues and couldn't find a solution or duplication
• I already searched in Google and didn't find any good information or help
• I looked at the docs and didn't see anything to help

What happened?

There is no documentation covering package_spec which is used in several commands e.g. install, create, and update.

conda/conda/cli/conda_argparse.py

Lines 1341 to 1347 in 55cd442

	p.add_argument(
	'packages',
	metavar='package_spec',
	action="store",
	nargs='*',
	help="Packages to install or update in the conda environment.",
	)

The documentation can be found in https://docs.conda.io/projects/conda-build/en/latest/resources/package-spec.html#package-match-specifications
Should the documentation be added to this repository?
Should a reference be made into the conda-build documentation?

Conda info

Not relevant.

Conda config

Not relevant

Conda list

Not relevant

Additional Context

Not relevant

[github-actions]

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Thanks!

[roccomoretti]

Agree that some sort of cross-reference for the package specification syntax specification should show up in https://docs.conda.io/projects/conda/en/latest/commands/install.html

Related to this, if https://github.com/conda/conda/blob/main/docs/source/user-guide/concepts/pkg-specs.rst#package-match-specifications is the relevant documentation, it has rather confusing phrasing -- At the top it states: "This match specification is not the same as the syntax used at the command line with conda install", but then later on it gives examples that explicitly uses conda install. It's unclear what "is not the same" implies about the syntax in various use cases.