Default project versioning in Scala SBT is very simple. All you need is to set version parameter in build.sbt file:

version := 0.0.1

Unfortunately it has few near fatal flaws:

1. You would have to remember to change version number in build file once it’s “ready”;
2. If you use git (you should), then you would probably have to maintain version number in few places (and try to keep it in sync too);
3. The command to get the only version number in sbt is quite ugly and verbose (ok, maybe this one is not that fatal):

sbt -no-colors --info "version" | tail -1 | sed 's/\[info\]\ //'

Wouldn’t it be cool if SBT would be able to determine version number from git tags?

Thankfully there is a plugin just for that and it’s called sbt-git.

Installation

is very trivial and is exactly what you would need to do for most of other sbt plugins.

Add plugin dependency at project/plugins.sbt:

addSbtPlugin("com.typesafe.sbt" % "sbt-git" % "0.9.3")

Enable it in build.sbt:

enablePlugins(GitVersioning)

Git tag version matching rules

1. It requires tags to start with “v” (by default, this can be configured otherwise);
2. When there are no matching tags or when current commit is not tagged, then it will use full commit sha like this one: 1ba5dc155ff1ff1436905f20100d60af92b1d4cb;
3. When there is matching tag, then it will be used as a version (minus the “v”) - 0.0.1 for tag v0.0.1;
4. When current commit is tagged, but there are changes to tracked files, then it will use “-SNAPSHOT” suffix, like 0.0.1-SNAPSHOT.

There are other version matching rules and example matching customisation in original documentation (for instance, to match any tag starting with a number, not requiring the “v” prefix anymore).

So is it any good?

Sbt-git is great in context of continuous delivery and automation:

1. You don’t have to change code to tag version number;
2. With sbt-git the git tags become the only version to maintain - no discrepancies;
3. Virtually any ci environment supports git, it’s easy to automate and there are tons of examples.

The plugin is well maintained and worked flawlessly in my case - highly recommended.