Simplify contrib/backport (go-gitea#27520)

This script was trying to be too smart, make it more straightforward and
less error-prone so that i could be used by the backport bot too
ideally.

- Always delete the backport branch so that script is idempotent in this
regard
- Remove the push functionality, it's best done by the user because only
they know the remote name
- Remove reading docs/config.yaml, it no longer exists
- Remove version detection, version is now a required argument
- Remove opening the pull request with xdg-open, xdg-open is not
portable
- Remove continue from failed cherry pick. It's best to reset manually
in this case
- Clean up the console logging

Example run:

```
$ go run ./contrib/backport --version v1.21 27503
* Backporting 27503 to origin/release/v1.21 as backport-27503-v1.21
* `git fetch origin main`
* `git fetch origin release/v1.21`
* `git branch -D backport-27503-v1.21`
* `git checkout -b backport-27503-v1.21 origin/release/v1.21`
* Attempting git cherry-pick 08efeb5
* Amending commit to prepend `Backport go-gitea#27503` to body
Backport done! You can now push it with `git push yourremote backport-27503-v1.21`
```

---------

Co-authored-by: delvh <dev.lh@web.de>

Author: silverwind

contrib/backport/backport.go

@@ -7,7 +7,6 @@ package main
 import (
 	"context"
 	"fmt"
-	"log"
 	"net/http"
 	"os"
 	"os/exec"
@@ -19,11 +18,8 @@ import (
 
 	"github.com/google/go-github/v53/github"
 	"github.com/urfave/cli/v2"
-	"gopkg.in/yaml.v3"
 )
 
-const defaultVersion = "v1.18" // to backport to
-
 func main() {
 	app := cli.NewApp()
 	app.Name = "backport"
@@ -54,16 +50,6 @@ func main() {
 			Name:  "backport-branch",
 			Usage: "Backport branch to backport on to (default: backport-<pr>-<version>",
 		},
-		&cli.StringFlag{
-			Name:  "remote",
-			Value: "",
-			Usage: "Remote for your fork of the Gitea upstream",
-		},
-		&cli.StringFlag{
-			Name:  "fork-user",
-			Value: "",
-			Usage: "Forked user name on Github",
-		},
 		&cli.BoolFlag{
 			Name:  "no-fetch",
 			Usage: "Set this flag to prevent fetch of remote branches",
@@ -72,18 +58,6 @@ func main() {
 			Name:  "no-amend-message",
 			Usage: "Set this flag to prevent automatic amendment of the commit message",
 		},
-		&cli.BoolFlag{
-			Name:  "no-push",
-			Usage: "Set this flag to prevent pushing the backport up to your fork",
-		},
-		&cli.BoolFlag{
-			Name:  "no-xdg-open",
-			Usage: "Set this flag to not use xdg-open to open the PR URL",
-		},
-		&cli.BoolFlag{
-			Name:  "continue",
-			Usage: "Set this flag to continue from a git cherry-pick that has broken",
-		},
 	}
 	cli.AppHelpTemplate = `NAME:
 	{{.Name}} - {{.Usage}}
@@ -101,49 +75,24 @@ OPTIONS:
 	app.Action = runBackport
 
 	if err := app.Run(os.Args); err != nil {
-		fmt.Fprintf(os.Stderr, "Unable to backport: %v\n", err)
+		fmt.Fprintf(os.Stderr, "%v\n", err)
 	}
 }
 
 func runBackport(c *cli.Context) error {
 	ctx, cancel := installSignals()
 	defer cancel()
 
-	continuing := c.Bool("continue")
-
-	var pr string
-
 	version := c.String("version")
-	if version == "" && continuing {
-		// determine version from current branch name
-		var err error
-		pr, version, err = readCurrentBranch(ctx)
-		if err != nil {
-			return err
-		}
-	}
 	if version == "" {
-		version = readVersion()
-	}
-	if version == "" {
-		version = defaultVersion
+		return fmt.Errorf("Provide a version to backport to")
 	}
 
 	upstream := c.String("upstream")
 	if upstream == "" {
 		upstream = "origin"
 	}
 
-	forkUser := c.String("fork-user")
-	remote := c.String("remote")
-	if remote == "" && !c.Bool("--no-push") {
-		var err error
-		remote, forkUser, err = determineRemote(ctx, forkUser)
-		if err != nil {
-			return err
-		}
-	}
-
 	upstreamReleaseBranch := c.String("release-branch")
 	if upstreamReleaseBranch == "" {
 		upstreamReleaseBranch = path.Join("release", version)
@@ -152,14 +101,12 @@ func runBackport(c *cli.Context) error {
 	localReleaseBranch := path.Join(upstream, upstreamReleaseBranch)
 
 	args := c.Args().Slice()
-	if len(args) == 0 && pr == "" {
-		return fmt.Errorf("no PR number provided\nProvide a PR number to backport")
-	} else if len(args) != 1 && pr == "" {
-		return fmt.Errorf("multiple PRs provided %v\nOnly a single PR can be backported at a time", args)
-	}
-	if pr == "" {
-		pr = args[0]
+	if len(args) == 0 {
+		return fmt.Errorf("Provide a PR number to backport")
+	} else if len(args) != 1 {
+		return fmt.Errorf("Only a single PR can be backported at a time")
 	}
+	pr := args[0]
 
 	backportBranch := c.String("backport-branch")
 	if backportBranch == "" {
@@ -186,10 +133,8 @@ func runBackport(c *cli.Context) error {
 		}
 	}
 
-	if !continuing {
-		if err := checkoutBackportBranch(ctx, backportBranch, localReleaseBranch); err != nil {
-			return err
-		}
+	if err := checkoutBackportBranch(ctx, backportBranch, localReleaseBranch); err != nil {
+		return err
 	}
 
 	if err := cherrypick(ctx, sha); err != nil {
@@ -202,41 +147,8 @@ func runBackport(c *cli.Context) error {
 		}
 	}
 
-	if !c.Bool("no-push") {
-		url := "https://github.com/go-gitea/gitea/compare/" + upstreamReleaseBranch + "..." + forkUser + ":" + backportBranch
-
-		if err := gitPushUp(ctx, remote, backportBranch); err != nil {
-			return err
-		}
-
-		if !c.Bool("no-xdg-open") {
-			if err := xdgOpen(ctx, url); err != nil {
-				return err
-			}
-		} else {
-			fmt.Printf("* Navigate to %s to open PR\n", url)
-		}
-	}
-	return nil
-}
-
-func xdgOpen(ctx context.Context, url string) error {
-	fmt.Printf("* `xdg-open %s`\n", url)
-	out, err := exec.CommandContext(ctx, "xdg-open", url).Output()
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "%s", string(out))
-		return fmt.Errorf("unable to xdg-open to %s: %w", url, err)
-	}
-	return nil
-}
+	fmt.Printf("Backport done! You can now push it with `git push <your remote> %s`\n", backportBranch)
 
-func gitPushUp(ctx context.Context, remote, backportBranch string) error {
-	fmt.Printf("* `git push -u %s %s`\n", remote, backportBranch)
-	out, err := exec.CommandContext(ctx, "git", "push", "-u", remote, backportBranch).Output()
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "%s", string(out))
-		return fmt.Errorf("unable to push up to %s: %w", remote, err)
-	}
 	return nil
 }
 
@@ -267,18 +179,6 @@ func amendCommit(ctx context.Context, pr string) error {
 }
 
 func cherrypick(ctx context.Context, sha string) error {
-	// Check if a CHERRY_PICK_HEAD exists
-	if _, err := os.Stat(".git/CHERRY_PICK_HEAD"); err == nil {
-		// Assume that we are in the middle of cherry-pick - continue it
-		fmt.Println("* Attempting git cherry-pick --continue")
-		out, err := exec.CommandContext(ctx, "git", "cherry-pick", "--continue").Output()
-		if err != nil {
-			fmt.Fprintf(os.Stderr, "git cherry-pick --continue failed:\n%s\n", string(out))
-			return fmt.Errorf("unable to continue cherry-pick: %w", err)
-		}
-		return nil
-	}
-
 	fmt.Printf("* Attempting git cherry-pick %s\n", sha)
 	out, err := exec.CommandContext(ctx, "git", "cherry-pick", sha).Output()
 	if err != nil {
@@ -289,22 +189,8 @@ func cherrypick(ctx context.Context, sha string) error {
 }
 
 func checkoutBackportBranch(ctx context.Context, backportBranch, releaseBranch string) error {
-	out, err := exec.CommandContext(ctx, "git", "branch", "--show-current").Output()
-	if err != nil {
-		return fmt.Errorf("unable to check current branch %w", err)
-	}
-
-	currentBranch := strings.TrimSpace(string(out))
-	fmt.Printf("* Current branch is %s\n", currentBranch)
-	if currentBranch == backportBranch {
-		fmt.Printf("* Current branch is %s - not checking out\n", currentBranch)
-		return nil
-	}
-
-	if _, err := exec.CommandContext(ctx, "git", "rev-list", "-1", backportBranch).Output(); err == nil {
-		fmt.Printf("* Branch %s already exists. Checking it out...\n", backportBranch)
-		return exec.CommandContext(ctx, "git", "checkout", "-f", backportBranch).Run()
-	}
+	fmt.Printf("* `git branch -D %s`\n", backportBranch)
+	_ = exec.CommandContext(ctx, "git", "branch", "-D", backportBranch).Run()
 
 	fmt.Printf("* `git checkout -b %s %s`\n", backportBranch, releaseBranch)
 	return exec.CommandContext(ctx, "git", "checkout", "-b", backportBranch, releaseBranch).Run()
@@ -317,116 +203,17 @@ func fetchRemoteAndMain(ctx context.Context, remote, releaseBranch string) error
 		fmt.Println(string(out))
 		return fmt.Errorf("unable to fetch %s from %s: %w", "main", remote, err)
 	}
-	fmt.Println(string(out))
 
 	fmt.Printf("* `git fetch %s %s`\n", remote, releaseBranch)
 	out, err = exec.CommandContext(ctx, "git", "fetch", remote, releaseBranch).Output()
 	if err != nil {
 		fmt.Println(string(out))
 		return fmt.Errorf("unable to fetch %s from %s: %w", releaseBranch, remote, err)
 	}
-	fmt.Println(string(out))
 
 	return nil
 }
 
-func determineRemote(ctx context.Context, forkUser string) (string, string, error) {
-	out, err := exec.CommandContext(ctx, "git", "remote", "-v").Output()
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Unable to list git remotes:\n%s\n", string(out))
-		return "", "", fmt.Errorf("unable to determine forked remote: %w", err)
-	}
-	lines := strings.Split(string(out), "\n")
-	for _, line := range lines {
-		fields := strings.Split(line, "\t")
-		name, remote := fields[0], fields[1]
-		// only look at pushers
-		if !strings.HasSuffix(remote, " (push)") {
-			continue
-		}
-		// only look at github.com pushes
-		if !strings.Contains(remote, "github.com") {
-			continue
-		}
-		// ignore go-gitea/gitea
-		if strings.Contains(remote, "go-gitea/gitea") {
-			continue
-		}
-		if !strings.Contains(remote, forkUser) {
-			continue
-		}
-		if strings.HasPrefix(remote, "git@github.com:") {
-			forkUser = strings.TrimPrefix(remote, "git@github.com:")
-		} else if strings.HasPrefix(remote, "https://github.com/") {
-			forkUser = strings.TrimPrefix(remote, "https://github.com/")
-		} else if strings.HasPrefix(remote, "https://github.com/") {
-			forkUser = strings.TrimPrefix(remote, "https://github.com/")
-		} else if forkUser == "" {
-			return "", "", fmt.Errorf("unable to extract forkUser from remote %s: %s", name, remote)
-		}
-		idx := strings.Index(forkUser, "/")
-		if idx >= 0 {
-			forkUser = forkUser[:idx]
-		}
-		return name, forkUser, nil
-	}
-	return "", "", fmt.Errorf("unable to find appropriate remote in:\n%s", string(out))
-}
-
-func readCurrentBranch(ctx context.Context) (pr, version string, err error) {
-	out, err := exec.CommandContext(ctx, "git", "branch", "--show-current").Output()
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Unable to read current git branch:\n%s\n", string(out))
-		return "", "", fmt.Errorf("unable to read current git branch: %w", err)
-	}
-	parts := strings.Split(strings.TrimSpace(string(out)), "-")
-
-	if len(parts) != 3 || parts[0] != "backport" {
-		fmt.Fprintf(os.Stderr, "Unable to continue from git branch:\n%s\n", string(out))
-		return "", "", fmt.Errorf("unable to continue from git branch:\n%s", string(out))
-	}
-
-	return parts[1], parts[2], nil
-}
-
-func readVersion() string {
-	bs, err := os.ReadFile("docs/config.yaml")
-	if err != nil {
-		if err == os.ErrNotExist {
-			log.Println("`docs/config.yaml` not present")
-			return ""
-		}
-		fmt.Fprintf(os.Stderr, "Unable to read `docs/config.yaml`: %v\n", err)
-		return ""
-	}
-
-	type params struct {
-		Version string
-	}
-	type docConfig struct {
-		Params params
-	}
-	dc := &docConfig{}
-	if err := yaml.Unmarshal(bs, dc); err != nil {
-		fmt.Fprintf(os.Stderr, "Unable to read `docs/config.yaml`: %v\n", err)
-		return ""
-	}
-
-	if dc.Params.Version == "" {
-		fmt.Fprintf(os.Stderr, "No version in `docs/config.yaml`")
-		return ""
-	}
-
-	version := dc.Params.Version
-	if version[0] != 'v' {
-		version = "v" + version
-	}
-
-	split := strings.SplitN(version, ".", 3)
-
-	return strings.Join(split[:2], ".")
-}
-
 func determineSHAforPR(ctx context.Context, prStr string) (string, error) {
 	prNum, err := strconv.Atoi(prStr)
 	if err != nil {