Add version informations as a common package

[sdurrheimer]

Ref. prometheus/node_exporter#236

Usage as mentionned by @grobie

import (
    "flag"
    "fmt"
    "os"

    "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/common/log"
    "github.com/prometheus/common/version"
)

func init() {
    prometheus.MustRegister(version.NewCollector("<program>"))
}

func main() {
    var showVersion = flag.Bool("version", false, "Print version information.")
    flat.Parse()

    if *showVersion {
        fmt.Fprintln(os.Stdout, version.Print("<program>"))
        os.exit(0)
    }

    log.Infoln("Starting <program>", version.Info())
    log.Infoln("Build context", version.BuildContext())
}

I had a second implementation, but it was a bit overkill for a single metric.

[grobie]

Guess log might be a confusing name. Suggestions? VersionInfo?

[grobie]

version.Details()?

[sdurrheimer]

What about renaming :

• version.Info() to version.Print() or version.PrintString().
• version.VersionLog() to version.Info() or version.InfoString()
• version.BuildLog() to version.BuildContext() or version.BuildString()

[grobie]

Sounds good to me. I'd go with the first version, the return type should make clear it's a string.

[grobie]

👍 very nice!