feat(alpha update): add --git-config flag with clear defaults and replacement behavior

Assisted-by: ChatGPT (OpenAI)

Author: camilamacedo86

docs/book/src/reference/commands/alpha_update.md

@@ -53,6 +53,7 @@ The command creates three temporary branches:
     - `--preserve-path`: in squash mode, restore specific files (like CI configs) from your base branch.
     - `--output-branch`: pick a custom branch name.
     - `--push`: push the result to `origin` automatically.
+    - `--git-config`: sets git configurations.
 
 ### Step 5: Cleanup
 - Once the output branch is ready, all the temporary working branches are deleted.
@@ -132,19 +133,46 @@ make manifests generate fmt vet lint-fix
 make all
 ```
 
+### Changing Extra Git configs only during the run (does not change your ~/.gitconfig)_
+
+By default, `kubebuilder alpha update` applies safe Git configs:
+`merge.renameLimit=999999`, `diff.renameLimit=999999`.
+You can add more, or disable them.
+
+- **Add more on top of defaults**
+```shell
+kubebuilder alpha update \
+  --git-config merge.conflictStyle=diff3 \
+  --git-config rerere.enabled=true
+```
+
+- **Disable defaults entirely**
+```shell
+kubebuilder alpha update --git-config disable
+```
+
+- **Disable defaults and set your own**
+
+```shell
+kubebuilder alpha update \
+  --git-config disable \
+  --git-config rerere.enabled=true
+```
+
 ## Flags
 
-| Flag              | Description                                                                                                                                                 |
-|-------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| `--from-version`  | Kubebuilder release to update **from** (e.g., `v4.6.0`). If unset, read from the `PROJECT` file when possible.                                              |
-| `--to-version`    | Kubebuilder release to update **to** (e.g., `v4.7.0`). If unset, defaults to the latest available release.                                                  |
-| `--from-branch`   | Git branch that holds your current project code. Defaults to `main`.                                                                                        |
-| `--force`         | Continue even if merge conflicts happen. Conflicted files are committed with conflict markers (CI/cron friendly).                                           |
-| `--show-commits`  | Keep full history (do not squash). **Not compatible** with `--preserve-path`.                                                                               |
-| `--preserve-path` | Repeatable. **Squash mode only.** After copying the merge tree to the output branch, restore these paths from the base branch (e.g., `.github/workflows`).  |
-| `--output-branch` | Name of the output branch. Default: `kubebuilder-update-from-<from-version>-to-<to-version>`.                                                               |
-| `--push`          | Push the output branch to the `origin` remote after the update completes.                                                                                   |
-| `-h, --help`      | Show help for this command.                                                                                                                                 |
+| Flag              | Description                                                                                                                                                                                                                                                                                     |
+|-------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `--from-version`  | Kubebuilder release to update **from** (e.g., `v4.6.0`). If unset, read from the `PROJECT` file when possible.                                                                                                                                                                                  |
+| `--to-version`    | Kubebuilder release to update **to** (e.g., `v4.7.0`). If unset, defaults to the latest available release.                                                                                                                                                                                      |
+| `--from-branch`   | Git branch that holds your current project code. Defaults to `main`.                                                                                                                                                                                                                            |
+| `--force`         | Continue even if merge conflicts happen. Conflicted files are committed with conflict markers (CI/cron friendly).                                                                                                                                                                               |
+| `--show-commits`  | Keep full history (do not squash). **Not compatible** with `--preserve-path`.                                                                                                                                                                                                                   |
+| `--preserve-path` | Repeatable. **Squash mode only.** After copying the merge tree to the output branch, restore these paths from the base branch (e.g., `.github/workflows`).                                                                                                                                      |
+| `--output-branch` | Name of the output branch. Default: `kubebuilder-update-from-<from-version>-to-<to-version>`.                                                                                                                                                                                                   |
+| `--push`          | Push the output branch to the `origin` remote after the update completes.                                                                                                                                                                                                                       |
+| `--git-config`    | Repeatable. Pass per-invocation Git config as `-c key=value`. **Default** (if omitted): `-c merge.renameLimit=999999 -c diff.renameLimit=999999`. **Important**: if you pass this flag, your values **replace** the defaults. To keep them *and* add more, re-specify the defaults explicitly.  |
+| `-h, --help`      | Show help for this command.                                                                                                                                                                                                                                                                     |
 
 <aside class="note warning">
 <h1>You might need to upgrade your project first</h1>

pkg/cli/alpha/internal/update/helpers/git_commands.go

@@ -47,3 +47,13 @@ func CleanWorktree(label string) error {
 	}
 	return nil
 }
+
+// GitCmd creates a new git command with the provided git configuration
+func GitCmd(gitConfig []string, args ...string) *exec.Cmd {
+	gitArgs := make([]string, 0, len(gitConfig)*2+len(args))
+	for _, kv := range gitConfig {
+		gitArgs = append(gitArgs, "-c", kv)
+	}
+	gitArgs = append(gitArgs, args...)
+	return exec.Command("git", gitArgs...)
+}

pkg/cli/alpha/internal/update/update.go

@@ -77,6 +77,24 @@ type Update struct {
 	// CLI (`gh`) to be installed and authenticated in the local environment.
 	OpenGhIssue bool
 
+	// GitConfig contains per-invocation Git configurations that are applied
+	// to every `git` command via `git -c key=value`.
+	//
+	// Examples:
+	//   []string{"merge.renameLimit=999999"}               // enable robust rename detection
+	//   []string{"diff.renameLimit=999999"}                // improve diff rename detection
+	//   []string{"merge.conflictStyle=diff3"}              // show ancestor in conflict markers
+	//   []string{"rerere.enabled=true"}                    // enable reuse recorded resolutions
+	//
+	// Defaults:
+	//   If not set by the user, it defaults to:
+	//     []string{"merge.renameLimit=999999", "diff.renameLimit=999999"}
+	//
+	// Behavior:
+	//   If the user passes --git-config flags, those values REPLACE the defaults.
+	//   To keep defaults and add more, explicitly re-specify them alongside extras.
+	GitConfig []string
+
 	// Temporary branches created during the update process. These are internal to the run
 	// and are surfaced for transparency/debugging:
 	//   - AncestorBranch: clean scaffold generated from FromVersion
@@ -160,7 +178,7 @@ Resolve conflicts there, complete the merge locally, and push the branch.
 // This helps apply new scaffolding changes while preserving custom code.
 func (opts *Update) Update() error {
 	log.Info("Checking out base branch", "branch", opts.FromBranch)
-	checkoutCmd := exec.Command("git", "checkout", opts.FromBranch)
+	checkoutCmd := helpers.GitCmd(opts.GitConfig, "checkout", opts.FromBranch)
 	if err := checkoutCmd.Run(); err != nil {
 		return fmt.Errorf("failed to checkout base branch %s: %w", opts.FromBranch, err)
 	}
@@ -219,7 +237,7 @@ func (opts *Update) Update() error {
 	if opts.ShowCommits {
 		log.Info("Keeping commits history")
 		out := opts.getOutputBranchName()
-		if err := exec.Command("git", "checkout", "-b", out, opts.MergeBranch).Run(); err != nil {
+		if err := helpers.GitCmd(opts.GitConfig, "checkout", "-b", out, opts.MergeBranch).Run(); err != nil {
 			return fmt.Errorf("checkout %s: %w", out, err)
 		}
 	} else {
@@ -233,8 +251,8 @@ func (opts *Update) Update() error {
 	if opts.Push {
 		if opts.Push {
 			out := opts.getOutputBranchName()
-			_ = exec.Command("git", "checkout", out).Run()
-			if err := exec.Command("git", "push", "-u", "origin", out).Run(); err != nil {
+			_ = helpers.GitCmd(opts.GitConfig, "checkout", out).Run()
+			if err := helpers.GitCmd(opts.GitConfig, "push", "-u", "origin", out).Run(); err != nil {
 				return fmt.Errorf("failed to push %s: %w", out, err)
 			}
 		}
@@ -309,7 +327,7 @@ func (opts *Update) openGitHubIssue(hasConflicts bool) error {
 }
 
 func (opts *Update) cleanupTempBranches() {
-	_ = exec.Command("git", "checkout", opts.getOutputBranchName()).Run()
+	_ = helpers.GitCmd(opts.GitConfig, "checkout", opts.getOutputBranchName()).Run()
 
 	branches := []string{
 		opts.AncestorBranch,
@@ -324,8 +342,8 @@ func (opts *Update) cleanupTempBranches() {
 			continue
 		}
 		// Delete only if it's a LOCAL branch.
-		if err := exec.Command("git", "show-ref", "--verify", "--quiet", "refs/heads/"+b).Run(); err == nil {
-			_ = exec.Command("git", "branch", "-D", b).Run()
+		if err := helpers.GitCmd(opts.GitConfig, "show-ref", "--verify", "--quiet", "refs/heads/"+b).Run(); err == nil {
+			_ = helpers.GitCmd(opts.GitConfig, "branch", "-D", b).Run()
 		}
 	}
 }
@@ -345,7 +363,7 @@ func (opts *Update) preservePaths() {
 		if p == "" {
 			continue
 		}
-		if err := exec.Command("git", "checkout", opts.FromBranch, "--", p).Run(); err != nil {
+		if err := helpers.GitCmd(opts.GitConfig, "checkout", opts.FromBranch, "--", p).Run(); err != nil {
 			log.Warn("failed to restore preserved path", "path", p, "branch", opts.FromBranch, "error", err)
 		}
 	}
@@ -358,26 +376,26 @@ func (opts *Update) squashToOutputBranch(hasConflicts bool) error {
 	out := opts.getOutputBranchName()
 
 	// 1) base -> out
-	if err := exec.Command("git", "checkout", opts.FromBranch).Run(); err != nil {
+	if err := helpers.GitCmd(opts.GitConfig, "checkout", opts.FromBranch).Run(); err != nil {
 		return fmt.Errorf("checkout %s: %w", opts.FromBranch, err)
 	}
-	if err := exec.Command("git", "checkout", "-B", out, opts.FromBranch).Run(); err != nil {
+	if err := helpers.GitCmd(opts.GitConfig, "checkout", "-B", out, opts.FromBranch).Run(); err != nil {
 		return fmt.Errorf("create/reset %s from %s: %w", out, opts.FromBranch, err)
 	}
 
 	// 2) clean worktree, then copy merge tree
 	if err := helpers.CleanWorktree("output branch"); err != nil {
 		return fmt.Errorf("output branch: %w", err)
 	}
-	if err := exec.Command("git", "checkout", opts.MergeBranch, "--", ".").Run(); err != nil {
+	if err := helpers.GitCmd(opts.GitConfig, "checkout", opts.MergeBranch, "--", ".").Run(); err != nil {
 		return fmt.Errorf("checkout %s content: %w", "merge", err)
 	}
 
 	// 3) optionally restore preserved paths from base (tests assert on 'git restore …')
 	opts.preservePaths()
 
 	// 4) stage and single squashed commit
-	if err := exec.Command("git", "add", "--all").Run(); err != nil {
+	if err := helpers.GitCmd(opts.GitConfig, "add", "--all").Run(); err != nil {
 		return fmt.Errorf("stage output: %w", err)
 	}
 
@@ -404,7 +422,7 @@ func regenerateProjectWithVersion(version string) error {
 // prepareAncestorBranch prepares the ancestor branch by checking it out,
 // cleaning up the project files, and regenerating the project with the specified version.
 func (opts *Update) prepareAncestorBranch() error {
-	if err := exec.Command("git", "checkout", "-b", opts.AncestorBranch, opts.FromBranch).Run(); err != nil {
+	if err := helpers.GitCmd(opts.GitConfig, "checkout", "-b", opts.AncestorBranch, opts.FromBranch).Run(); err != nil {
 		return fmt.Errorf("failed to create %s from %s: %w", opts.AncestorBranch, opts.FromBranch, err)
 	}
 	if err := cleanupBranch(); err != nil {
@@ -413,7 +431,7 @@ func (opts *Update) prepareAncestorBranch() error {
 	if err := regenerateProjectWithVersion(opts.FromVersion); err != nil {
 		return fmt.Errorf("failed to regenerate project with fromVersion %s: %w", opts.FromVersion, err)
 	}
-	gitCmd := exec.Command("git", "add", "--all")
+	gitCmd := helpers.GitCmd(opts.GitConfig, "add", "--all")
 	if err := gitCmd.Run(); err != nil {
 		return fmt.Errorf("failed to stage changes in %s: %w", opts.AncestorBranch, err)
 	}
@@ -488,17 +506,17 @@ func envWithPrefixedPath(dir string) []string {
 // populates it with the user's actual project content from the default branch.
 // This represents the current state of the user's project.
 func (opts *Update) prepareOriginalBranch() error {
-	gitCmd := exec.Command("git", "checkout", "-b", opts.OriginalBranch)
+	gitCmd := helpers.GitCmd(opts.GitConfig, "checkout", "-b", opts.OriginalBranch)
 	if err := gitCmd.Run(); err != nil {
 		return fmt.Errorf("failed to checkout branch %s: %w", opts.OriginalBranch, err)
 	}
 
-	gitCmd = exec.Command("git", "checkout", opts.FromBranch, "--", ".")
+	gitCmd = helpers.GitCmd(opts.GitConfig, "checkout", opts.FromBranch, "--", ".")
 	if err := gitCmd.Run(); err != nil {
 		return fmt.Errorf("failed to checkout content from %s branch onto %s: %w", opts.FromBranch, opts.OriginalBranch, err)
 	}
 
-	gitCmd = exec.Command("git", "add", "--all")
+	gitCmd = helpers.GitCmd(opts.GitConfig, "add", "--all")
 	if err := gitCmd.Run(); err != nil {
 		return fmt.Errorf("failed to stage all changes in current: %w", err)
 	}
@@ -515,13 +533,13 @@ func (opts *Update) prepareOriginalBranch() error {
 // generates fresh scaffolding using the current (latest) CLI version.
 // This represents what the project should look like with the new version.
 func (opts *Update) prepareUpgradeBranch() error {
-	gitCmd := exec.Command("git", "checkout", "-b", opts.UpgradeBranch, opts.AncestorBranch)
+	gitCmd := helpers.GitCmd(opts.GitConfig, "checkout", "-b", opts.UpgradeBranch, opts.AncestorBranch)
 	if err := gitCmd.Run(); err != nil {
 		return fmt.Errorf("failed to checkout %s branch off %s: %w",
 			opts.UpgradeBranch, opts.AncestorBranch, err)
 	}
 
-	checkoutCmd := exec.Command("git", "checkout", opts.UpgradeBranch)
+	checkoutCmd := helpers.GitCmd(opts.GitConfig, "checkout", opts.UpgradeBranch)
 	if err := checkoutCmd.Run(); err != nil {
 		return fmt.Errorf("failed to checkout base branch %s: %w", opts.UpgradeBranch, err)
 	}
@@ -532,7 +550,7 @@ func (opts *Update) prepareUpgradeBranch() error {
 	if err := regenerateProjectWithVersion(opts.ToVersion); err != nil {
 		return fmt.Errorf("failed to regenerate project with version %s: %w", opts.ToVersion, err)
 	}
-	gitCmd = exec.Command("git", "add", "--all")
+	gitCmd = helpers.GitCmd(opts.GitConfig, "add", "--all")
 	if err := gitCmd.Run(); err != nil {
 		return fmt.Errorf("failed to stage changes in %s: %w", opts.UpgradeBranch, err)
 	}
@@ -546,17 +564,17 @@ func (opts *Update) prepareUpgradeBranch() error {
 // mergeOriginalToUpgrade attempts to merge the upgrade branch
 func (opts *Update) mergeOriginalToUpgrade() (bool, error) {
 	hasConflicts := false
-	if err := exec.Command("git", "checkout", "-b", opts.MergeBranch, opts.UpgradeBranch).Run(); err != nil {
+	if err := helpers.GitCmd(opts.GitConfig, "checkout", "-b", opts.MergeBranch, opts.UpgradeBranch).Run(); err != nil {
 		return hasConflicts, fmt.Errorf("failed to create merge branch %s from %s: %w",
 			opts.MergeBranch, opts.UpgradeBranch, err)
 	}
 
-	checkoutCmd := exec.Command("git", "checkout", opts.MergeBranch)
+	checkoutCmd := helpers.GitCmd(opts.GitConfig, "checkout", opts.MergeBranch)
 	if err := checkoutCmd.Run(); err != nil {
 		return hasConflicts, fmt.Errorf("failed to checkout base branch %s: %w", opts.MergeBranch, err)
 	}
 
-	mergeCmd := exec.Command("git", "merge", "--no-edit", "--no-commit", opts.OriginalBranch)
+	mergeCmd := helpers.GitCmd(opts.GitConfig, "merge", "--no-edit", "--no-commit", opts.OriginalBranch)
 	err := mergeCmd.Run()
 	if err != nil {
 		var exitErr *exec.ExitError
@@ -584,7 +602,7 @@ func (opts *Update) mergeOriginalToUpgrade() (bool, error) {
 	runMakeTargets()
 
 	// Step 4: Stage and commit
-	if err := exec.Command("git", "add", "--all").Run(); err != nil {
+	if err := helpers.GitCmd(opts.GitConfig, "add", "--all").Run(); err != nil {
 		return hasConflicts, fmt.Errorf("failed to stage merge results: %w", err)
 	}