Restore repositories-btrfs of a full BTRFS parition of Docker

gen_repositories_btrfs.go

package main

// docker images --no-trunc | awk '{print $1 " " $2 " " $3}' > images_data
// go run gen_repositories_btrfs.go images_data

import (
        "bufio"
        "bytes"
        "encoding/json"
        "fmt"
        "io/ioutil"
        "os"
        "strings"
)

func main() {
        content, _ := ioutil.ReadFile(os.Args[1])
        contentReader := bytes.NewReader(content)
        reader := bufio.NewReader(contentReader)

        images := map[string]map[string]string{}
        var err error
        for err == nil {
                var line []byte
                line, _, err = reader.ReadLine()
                if string(line) == "" {
                        break
                }
                fields := strings.Split(string(line), " ")
                imageTags, ok := images[fields[0]]
                if ok {
                        imageTags[fields[1]] = fields[2]
                } else {
                        imageTags = map[string]string{fields[1]: fields[2]}
                }
                images[fields[0]] = imageTags
        }

        header := map[string]interface{}{"Repositories": images}
        js, _ := json.Marshal(header)
        fmt.Println(string(js))
}