feat: add a step that logs the version of lake and lean

[oliver-butterley]

Add a step to the action which:

• reports if mathlib is used
• reports the lake version
• reports the lean version

resolves #12

[oliver-butterley]

Give me some feedback about precisely what behaviour is required and I can modify this.

• Current output is as seen in attached images.
• Since this is the first time that lake and lean are used it also shows them being obtained by elan. T
• Concerning the mathlib check, there are three options: true, false, not checked. In order to get the tested for and false option the corresponding sh file was modified.
• In the case of mathlib dependency not being checked, currently displays "" but could be modified to be more communicative if required. Alternatively always run the mathlib check, whatever the setting of mathlib-cache. (And hopefully the lake CLI is improved soon and there is more elegance to accessing the lean project info.)

[austinletson]

This PR looks great! This will allow existing projects such as import-graph to simplify their workflow even more by using lean-action.

I have a suggestion that might improve the user experience, though it deviates slightly from the original issue. Since some Lean setup happens during lean --version/lake --version, should we incorporate this logging into the install elan step, perhaps renaming it to setup lean? This would:

• Contain any Lean installation issues within the setup lean step, making troubleshooting easier.
• Provide users who don't need version details a cleaner workflow.

If we decide to go this route, we could potentially omit the Mathlib check logging since the detect Mathlib step already covers it.

Let me know what you think!

[oliver-butterley]

I like your plan, simplicity is a good thing.

[oliver-butterley]

😱 I'm sorry! I'm perfectly aware of this issue with the paths in gh actions and I also thought I was testing each thing I did before opening the PR. However it appears that I wasn't capable of anything sensible late on Friday after a long week. I'll mend it carefully soon. Probably simplest to just add the paths to each command, e.g., .elan/bin/lean --version.

[oliver-butterley]

I've updated these two lines to log the version. I tested it on a test repo and it does as expected.

[austinletson]

Looks great. Thanks @oliver-butterley!