avoid downloading dagger if requested version is already installed

[kpenfound]

Fixes #164

Check for an existing dagger install, and if its version matches the requested version, skip the installation step

[jedevc]

SGTM, but I think we could maybe avoid an error if the version if the right version of dagger is already installed?

[kpenfound]

@jedevc thats the dilemma, right now it doesn't care about the version at all, only whether there is already a dagger binary in the path, and there is no error state. so you have:

preinstalled version	requested version	result without force-install	result with force-install
foo	bar	foo	bar
none	bar	bar	bar
foo	foo	foo (skipped)	foo (downloaded)

my goal was to avoid error states, but we also don't want surprising behavior. The thinking is that if you have dagger pre-installed, you probably expect it to be there. If you want to override that with a specific version, there's a path to do that

[jedevc]

I think the thing that confuses me with the table is that you can request bar and end up in a state where you're actually running foo.

IMO, if you set bar, then you should always get bar - that's the behavior on main today (by essentially always forcing the install).

My suggestion would be to detect the version of the currently installed dagger, and check if it's the requested version (mildly annoying for commit builds off of main, but probably still doable). If it's the request version, skip, if not, then either, no particular preference:

• Overwrite it
• Error

I think that means that we wouldn't have a force-install option anymore?

[kpenfound]

@jedevc yeah we can definitely do that, I saw the script linked in the original issue. What I'm confused about in that case is why this was a blocker for using this action in dagger/dagger @matipan . Is it really about avoiding the ~18mb download?

[kpenfound]

@jedevc @matipan updated based on our live discussion!