Tag

Magefile support for tagging and releasing at Invopop.

Installation

go get github.com/invopop/tag

Releasing

Example mage.go file:

//go:build mage
// +build mage

package main

import (
	"github.com/invopop/tag"
)

// Release a new version based on the current branch and timestamp.
func Release() error {
	return tag.Release()
}

Running mage release will:

1. Fail if there are uncommitted changes.
2. Tag the current commit with a timestamp-based version, unless it's already tagged.
3. Push tags to the remote.

Versions use the UTC time of the release. Commits on main get the bare timestamp, and other branches are prefixed with the branch name. Characters that aren't valid in git or Docker tags, such as /, are replaced with -:

Branch	Tag
main	v20260923T1504
fix-login	fix-login-v20260923T1504
feat/new-thing	feat-new-thing-v20260923T1504

Build Information

tag.Now() collects details about the current build from git, and can be used to embed version information in binaries at build time:

// Build the application with version details embedded.
func Build() error {
	return sh.Run("go", "build", "-ldflags", tag.Now().LDFlags(), "./cmd/app")
}

This sets the BuildVersion and BuildTime variables in your main package, which must be declared:

package main

var (
	BuildVersion = "dev"
	BuildTime    = ""
)

Version() returns the current tag if the commit has one. Otherwise it returns <branch>-<short-commit>, with a -WIP suffix if there are uncommitted changes. Outside a git repository, such as in some CI environments, it falls back to the VERSION environment variable.