Purpose and Motivation

Before this PR, the "About" dialog in the IDE of the release (tagged) builds would report Built from branch 'HEAD' [<SHA>]. After this PR, the dialog reads Built from tag '<tag-name>' [<SHA>]. The non-tagged builds display the branch name as they have previously.

Here are the dialogs from builds from this branch and from a temporary tag:

For a tagged commit, the beginning of cmake config now looks like this:

$ cmake ..
-- SuperCollider Version: 3.13.0-dev
-- Building from tag Version-3.13.0-testTagName, commit hash is 354b10d266
-- Please specify the build configuration in the next step

API change...?

There is a very slight change to the response in the server API, if we even consider this a change. Previously, for the release builds the response to the /version message would include HEAD as the branch name, while currently it returns the tag name. These fields are marked in the help as informational only, so I don't believe it's an actual issue, but I wanted to point it out for the completeness sake

s.boot;
OSCFunc.trace(true, true);
s.sendMsg(\version);

Response:

OSC Message Received:
	time: 46.35657025
	address: a NetAddr(127.0.0.1, 57110)
	recvPort: 57120
	msg: [ /version.reply, scsynth, 3, 13, .0-dev, Version-3.13.0-testTagName, 354b10d266 ]

Types of changes

• New feature
• Breaking change (not really, but...)

To-do list

• Code is tested
• All tests are passing
• Updated documentation
• This PR is ready for review