Show git commit if version information is missing

[Limero]

This uses runtime/debug to show the Go version and Git commit embedded in the binary if version information is missing. The previous behavior is to just print nothing if the version is missing which is not very helpful.

I also considered adding the Go version information to the regular version information, but decided against it in case someone parses the output from the current version command.

Example output of custom built binary:

Go version: go1.21.4
Commit: 4f8ba9726d0bb6af4904740b52ba7b18320709ee 2023-12-02T04:17:13Z modified

[joelim-work]

Thanks very much for this patch, I think this will be helpful for bug reports.

One minor thing is that I'm not sure how useful vcs.time is, although I guess it can't hurt to include it anyway. Otherwise I don't have much opinion on the format of the version output, and overall the PR looks fine to me.

[Limero]

Thanks very much for this patch, I think this will be helpful for bug reports.

One minor thing is that I'm not sure how useful vcs.time is, although I guess it can't hurt to include it anyway. Otherwise I don't have much opinion on the format of the version output, and overall the PR looks fine to me.

Thanks for reviewing! I actually find the vcs.time quite useful, being able to see how old your current build is right away without having to manually look up the commit

[joelim-work]

Thanks for reviewing! I actually find the vcs.time quite useful, being able to see how old your current build is right away without having to manually look up the commit

Cool no worries, I will give my approval then. Thanks once again.

[ilyagr]

Thanks for the PR!

Two minor suggestions:

• Put the Go line after the Commit line
• (Optional) Instead of Commit:, I would write Built at commit . Or, alternatively, you could have 3 lines: 1) Just the commit id, "Commit date:" line, and "Go version:" line.

I was also thinking about an alternative plan: --version could just print the commit id, and there could be a separate --verbose-version option to print everything (including the official version, if present). However, I decided we don't really have to think about that too hard now. We can merge this and then see whether there's a demand for something more complicated.

[Limero]

@ilyagr Thanks! I've updated the format to now look like the followng:

Built at commit: 397f4a089030e7df9ceca5973523ae5a4453c415 (dirty) 2023-12-02T04:21:57Z
Go version: go1.21.4

[ilyagr]

Thank you! LGTM.