monorepo support for git application version

[tsloughter]

vsn in the .app.src file should support a string that is a prefix passed to git describe in the argument --match.

{vsn, {git, "api-*"}}

Then the prefix should be stripped to create the application version.

This helps use of the feature in repos with multiple applications.

Looking at this code again I also don't know why we don't just use git describe --tags and let git do all the work. That is a separate issue, but I'm guessing maybe git describe worked different way back when this was created and it was never updated.

[ferd]

The version can be a string and we use, sometimes, commit hashes for this. So I imagine git describe --tags wouldn't do a good job of that, since we want build sub-versions even for non-tag values.

We currently support git, {git, short|long}, it might make sense to also restrict this to {git, tag|{tag, Filter}} or something.

The other question I have is that since this is likely a thing you need for OTel which has many releases, do you expect the filter to pick a subset? Afaict the --match syntax supports glob syntax, which means by default you would get the newest tag matching api-1.2.3 and it would contain the prefix in it. Is the prefix a thing you want kept in? I know we had issues in the past where some of our common deps had tags like v1.2.3 and the v was automatically stripped, so it would be interesting to know if there's a need to make that stripping explicit.

[tsloughter]

I'd want to strip the prefix.

And right, would want this for otel. I want to better script/automate releasing and a sore spot is versioning.