Expose version info in CLI tool with build-time obtained git hash

[jsdw]

Builds off @DaviRain-Su's work in #776 and provides version info in the subxt CLI command, making the git hash be a compile-time included string.

Closes #739

[niklasad1]

you could do something similar as substrate to get a better error message if git fails:

		match Command::new("git").args(&["rev-parse", "--short=11", "HEAD"]).output() {
			Ok(o) if o.status.success() => {
				let sha = String::from_utf8_lossy(&o.stdout).trim().to_owned();
				Cow::from(sha)
			},
			Ok(o) => {
				println!("cargo:warning=Git command failed with status: {}", o.status);
				Cow::from("unknown")
			},
			Err(err) => {
				println!("cargo:warning=Failed to execute git command: {}", err);
				Cow::from("unknown")
			},
		}

I guess you want to fail the entire thing once it errors, I have no issues with that :)

[niklasad1]

Perhaps the expect output is clear enough not sure

[jsdw]

Nice idea! I'd never expect the git tool not to exist really in a build env I guess, but maybe worth doing this just incase! :)

[jsdw]

I added this; nice suggestion!

[niklasad1]

You could have cherry-picked @DaviRain-Su commit to give him some kudos for the work but yeah kudos in the PR description works as well I guess :P

[jsdw]

You could have cherry-picked @DaviRain-Su commit to give him some kudos for the work but yeah kudos in the PR description works as well I guess :P

I'll remember that for next time; I wanted to give kudos for sure, but it's a pain working with remote branches so I was lazy :)

[jsdw]

I haven't merged this yet because I'm playing with rerun-if-changed and for some reason if I push a commit to the repo and then rebuild, this script doesn't update the version properly. Am looking into it!

[jsdw]

It took me far too long to see that the rerun-if-changed commands I was using were wrong, but it all should work now :)