New tool to bump current_versions.sh automatically

This commit contains a new utility that helps to automate a version bump
for sandbox.

You can run this command to get the vibe of what it does.

```
$ go run cmd/bump-version/main.go -help
```

In order to try it out you can run this command form sandbox root. By
default it won't overwrite anything. It will print to stdout a new
version of the current_versions.sh file where all the images are
calculate cloning the various repositories

```
$ go run cmd/bump-version/main.go
```

If you want to overwrite the current_versions file you can use the flag
`-overwrite`.

More will come but for now, that's the PoC. Ideally this can be hooked
to CI/CD and run periodically, opening a PR that can be evaluated and
merged.

Signed-off-by: Gianluca Arbezzano <gianarb92@gmail.com>

cmd/bump-version/main.go

@@ -0,0 +1,155 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+
+	"github.com/pkg/errors"
+	"github.com/tinkerbell/sandbox/cmd/bump-version/envfile"
+	"github.com/tinkerbell/sandbox/cmd/bump-version/git"
+	"github.com/tinkerbell/sandbox/cmd/bump-version/image"
+)
+
+// Config represents the flags that you can configure
+// when running bump-version
+type Config struct {
+	// CurrentVersionFile is the path of the envfile that
+	// contains the current version of Tinkerbell stack.
+	// In sandbod it is called current_versions.sh
+	CurrentVersionFile string
+	// Overwrite switched the output of this program from
+	// standard output to the current_versions.sh file.
+	Overwrite bool
+	// Help prints the help command and exists
+	Help bool
+}
+
+const help = `
+bump-version is an utility that reads and update the current_version.sh file.
+It is designed to be used in CI/CD but it works locally as well.
+
+Note:
+    * Osie is currently not supported
+
+Examples:
+    Prints this -help
+
+    $ bump-version -help
+
+    This is how you will normally run this command.
+    bump-version will read the specified current-version-file
+    (./current_version.sh), it will clone the various components in memory
+    checking the latest commit available in the default branch.
+
+    The command will get and validate that a docker image is available for each
+    component and it will print the updated current_version.sh to stdout.
+
+    $ bump-version -current-version-file ./current_versions.sh
+
+    This command does the same as the previous one but it overwrite the content
+    of the original current_version file
+
+    $ bump-version -overwrite
+`
+
+const headerFile = `#!/bin/bash
+
+# This file is generated by an utility called bump-version in
+# tinkerbell/sandbox.
+# This file gets used from generate-envrc.sh but it is also used standalone by
+# automation that wants to get the version of the programs currently supported
+# in sandbox
+
+`
+
+func main() {
+	config := Config{}
+	fs := flag.NewFlagSet("bump-version", flag.ContinueOnError)
+	fs.BoolVar(&config.Help, "help", false, "Display help command and exit")
+	fs.BoolVar(&config.Overwrite, "overwrite", false, "This commands overwrite the current_versions file instead of printing to stdout")
+	fs.StringVar(&config.CurrentVersionFile, "current-version-file", "./current_versions.sh", "Load the current_version.sh file where the current Tinkerbell component versions are specified.")
+	err := fs.Parse(os.Args[1:])
+	if err != nil {
+		fmt.Fprint(os.Stderr, help)
+		log.Fatalf("Err: %s\n\r", err.Error())
+	}
+	if config.Help {
+		fmt.Fprint(os.Stderr, help)
+		os.Exit(0)
+	}
+	// Read the current_versions envfile
+	myEnv, err := envfile.ReadEnvFile(config.CurrentVersionFile)
+	if err != nil {
+		log.Fatal(errors.Wrap(err, "Impossible to read current_file.sh"))
+	}
+
+	tag, err := getImageTagFromRepo("https://github.com/tinkerbell/tink")
+	if err != nil {
+		log.Fatal(errors.Wrap(err, "Impossible to get image tag from tinkerbell/tink repo"))
+	}
+
+	// Set the new versions to the current_versions.sh
+	myEnv["TINKERBELL_TINK_SERVER_IMAGE"] = "quay.io/tinkerbell/tink:" + tag
+	myEnv["TINKERBELL_TINK_WORKER_IMAGE"] = "quay.io/tinkerbell/tink-worker:" + tag
+	myEnv["TINKERBELL_TINK_CLI_IMAGE"] = "quay.io/tinkerbell/tink-cli:" + tag
+
+	tag, err = getImageTagFromRepo("https://github.com/tinkerbell/hegel")
+	if err != nil {
+		log.Fatal(errors.Wrap(err, "Impossible to get image tag from tinkerbell/hegel repo"))
+	}
+
+	myEnv["TINKERBELL_TINK_HEGEL_IMAGE"] = "quay.io/tinkerbell/hegel:" + tag
+
+	tag, err = getImageTagFromRepo("https://github.com/tinkerbell/boots")
+	if err != nil {
+		log.Fatal(errors.Wrap(err, "Impossible to get image tag from tinkerbell/hegel repo"))
+	}
+
+	myEnv["TINKERBELL_TINK_BOOTS_IMAGE"] = "quay.io/tinkerbell/boots:" + tag
+
+	out, err := envfile.Marshal(myEnv)
+	if err != nil {
+		log.Fatal(errors.Wrap(err, "Impossible to render new current_version envfile"))
+	}
+
+	destination := os.Stdout
+	// if the overwrite flag is set to true change the output of the command
+	// from stdout to the original file
+	if config.Overwrite {
+		f, err := os.OpenFile(config.CurrentVersionFile, os.O_WRONLY|os.O_TRUNC, 0)
+		if err != nil {
+			log.Fatal(errors.Wrap(err, "Error overwriting current versions envfile"))
+		}
+		destination = f
+	}
+
+	io.WriteString(destination, headerFile+out+"\n")
+}
+
+// getImageTagFromRepo is an utility function that wraps a couple of things
+// together that technically we need to repeat for each repo.
+func getImageTagFromRepo(repoName string) (string, error) {
+	// Clone the specified repository in memory
+	repo, err := git.Clone(repoName)
+	if err != nil {
+		return "", errors.Wrap(err, "Impossible to clone the repository")
+	}
+
+	// Get the latest commit from the defautl branch
+	latestCommit, err := repo.GetHeadHash()
+	if err != nil {
+		return "", errors.Wrap(err, "Impossible to get commit from HEAD")
+	}
+
+	// Calculate the image tag from a commit sha
+	tag, err := image.TagFromSha(latestCommit)
+	if err != nil {
+		return "", errors.Wrap(err, "Impossible to get image tag from commit")
+	}
+
+	return tag, nil
+
+}