Start work on a command to self update kitty-tool

tools/cmd/tool/main.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"kitty/tools/cli"
 	"kitty/tools/cmd/at"
+	"kitty/tools/cmd/update_self"
 )
 
 var _ = fmt.Print
@@ -13,5 +14,6 @@ var _ = fmt.Print
 func KittyToolEntryPoints(root *cli.Command) {
 	// @
 	at.EntryPoint(root)
-
+	// update-self
+	update_self.EntryPoint(root)
 }

tools/cmd/update_self/main.go

@@ -0,0 +1,97 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package update_self
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+
+	"kitty/tools/cli"
+	"kitty/tools/tty"
+	"kitty/tools/tui"
+	"kitty/tools/utils"
+)
+
+var _ = fmt.Print
+
+type Options struct {
+	FetchVersion string
+}
+
+func fetch_latest_version() (string, error) {
+	b, err := utils.DownloadAsSlice("https://sw.kovidgoyal.net/kitty/current-version.txt", nil)
+	if err != nil {
+		return "", fmt.Errorf("Failed to fetch the latest available kitty version: %w", err)
+	}
+	return string(b), nil
+}
+
+func update_self(version string) (err error) {
+	exe := ""
+	exe, err = os.Executable()
+	if err != nil {
+		return fmt.Errorf("Failed to determine path to kitty-tool: %w", err)
+	}
+	exe, err = filepath.EvalSymlinks(exe)
+	if err != nil {
+		return err
+	}
+	rv := "v" + version
+	if version == "nightly" {
+		rv = version
+	}
+	if version == "latest" {
+		rv, err = fetch_latest_version()
+		if err != nil {
+			return
+		}
+	}
+	dest, err := os.CreateTemp(filepath.Dir(exe), "kitty-tool.")
+	if err != nil {
+		return err
+	}
+	defer func() { os.Remove(dest.Name()) }()
+
+	url := fmt.Sprintf("https://github.com/kovidgoyal/kitty/releases/download/%s/kitty-tool-%s-%s", rv, runtime.GOOS, runtime.GOARCH)
+	if !tty.IsTerminal(os.Stdout.Fd()) {
+		fmt.Println("Downloading:", url)
+		err = utils.DownloadToFile(exe, url, nil, nil)
+		if err != nil {
+			return err
+		}
+		fmt.Println("Downloaded to:", exe)
+	} else {
+		err = tui.DownloadFileWithProgress(exe, url, true)
+		if err != nil {
+			return err
+		}
+	}
+	return
+}
+
+func EntryPoint(root *cli.Command) {
+	sc := root.AddSubCommand(&cli.Command{
+		Name:             "update-self",
+		Usage:            "update-self [options ...]",
+		ShortDescription: "Update this kitty-tool binary",
+		HelpText:         "Update this kitty-tool binary in place to the latest available version.",
+		Run: func(cmd *cli.Command, args []string) (ret int, err error) {
+			if len(args) != 0 {
+				return 1, fmt.Errorf("No command line arguments are allowed")
+			}
+			opts := &Options{}
+			err = cmd.GetOptionValues(opts)
+			if err != nil {
+				return 1, err
+			}
+			return 0, update_self(opts.FetchVersion)
+		},
+	})
+	sc.Add(cli.OptionSpec{
+		Name:    "--fetch-version",
+		Default: "latest",
+		Help:    "The version to fetch. The special words :code:`latest` and :code:`nightly` fetch the latest stable and nightly release respectively. Other values can be, for example: 0.27.1.",
+	})
+}