Implement uv add

[charliermarsh]

As part of the Project API, we should have native add and remove commands.

[ibraheemdev]

#4193 provides the initial implementation. However, there are still some improvements and open questions:

• Accept unnamed URLs.
• Support dev dependencies with --dev.
• Support tool.uv.sources.
• Editable requirements?
• Should uv add perform a uv sync? If so, how should it propagate arguments like extras and dev deps?

[charliermarsh]

Also: adding dependencies that are extras.

[matterhorn103]

Excited for what's to come! Forgive my curiosity here. :) I almost asked this in #3560, where the differences and potential confusion between the planned commands uv tool add and uv tool install are discussed, but figured it's actually more relevant here.

Are you guys planning on a command that installs packages to the current venv (or system-wide, I guess) independent of a "project"-like setup? I.e. where there is no pyproject.toml present?

uv pip install is brilliant for standard package installation in this manner because of how fast it is, but your intention seems to be for the uv pip stuff to eventually only be a compatibility layer, rather than something that is regularly used.

But at the same time, if my impressions from your comments in various places are correct, a uv install command will be deliberately avoided?

Or will uv add work anyway without either needing a pyproject.toml or creating one?

[ibraheemdev]

Opened #4419 and #4418 to track the remaining tasks.

[ibraheemdev]

@matterhorn103 Yes, the new project APIs are structured specifically around pyproject.toml and uv.lock. The intention is you won't have to deal with lower level operations directly.