[nix] Show nix profile install progress

[mikeland73]

Summary

This shows inline progress when installing new packages (both global and local). nix profile install does this automatically but only in tty mode. @gcurtis curious if we can somehow make nix believe we're in tty mode without having to specify stdin and stdout?

Removed 2 blockers that are no longer needed:

• PackageInstallWriter is no longer needed I don't think. It could not see the lines it was meant to supress.
• Returning package not found is a bit redundant because all callsites of ProfileInstall already defensivelly check if package exists. If the user somehow does end up trying to install a package that doesn't exist, we still show a decent error

Fixed 2 semi-related errors:

• global add would print success message even if nothing was installed because of errors
• Removing a package from global devbox is impossible if the nix package was not installed

How was it tested?

devbox add curl hello bazel
devbox add global curl hello bazel

[savil]

Could you share a screenshot or video of what this looks like now? Not sure I am picturing it correctly. IIRC we needed the custom writer to indent the lines...

Removing a package from global devbox is impossible if the nix package was not installed

what could add a package to devbox.json but have it be not installed?

[savil]

Aside from ignoring some lines (which are no longer needed), I think we also needed this writer to indent the output:

_, err = io.WriteString(fw.Writer, "\t"+line+"\n")

[gcurtis]

We would need to specify stdout/stdin anyway because they default to /dev/null. The convention is to check if the stderr file descriptor is a tty, which is what I'm guessing Nix does. As long as the command's stderr is an *os.File pointing to a tty then it should work.

[mikeland73]

@savil it has to be a video or a gif because the output is dynamic inline. Which also means I don't think we need the indent to make it look good. Will share.

[mikeland73]

I'm a bit too lazy to make a video, this is what it looks like:

The lower line is dynamic and shows progress.

this is what it looks like after installing multiple packages

I went ahead and removed the redundant "package is now installed" and now it looks like

Two weird behavior nits:

• If package is already installed, no output.
• When installing local packages we also install the global ones which is weird.

Will address this in follow up