Revert "Do treeless clone for git clone to improve performance"

[Warashi]

Reverts #5722

The eventwatcher calls repo.CopyToModify every time, regardless of whether the event is registered.
This causes git clone from remote, e.g., GitHub, every time and costs network I/O.

The solution might be to call it CopyToModify only when the modification occurs.
For now, I revert the treeless clone because I don't have enough time to do so.

pipecd/pkg/app/piped/eventwatcher/eventwatcher.go

Lines 322 to 336 in 24a573d

	// execute inspects all Event-definition and handles the events per EventWatcherHandlerType if there are.
	func (w *watcher) execute(ctx context.Context, repo git.Repo, repoID string, eventCfgs []eventWatcherConfig) error {
	// Copy the repo to another directory to modify local file to avoid reverting previous changes.
	tmpDir, err := os.MkdirTemp(w.workingDir, "repo")
	if err != nil {
	w.logger.Error("failed to create a new temporary directory", zap.Error(err))
	return err
	}
	tmpRepo, err := repo.CopyToModify(filepath.Join(tmpDir, "tmp-repo"))
	if err != nil {
	w.logger.Error("failed to copy the repository to the temporary directory", zap.Error(err))
	return err
	}
	// nolint: errcheck
	defer tmpRepo.Clean()

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 27.88%. Comparing base (24a573d) to head (3fff308).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/git/repo.go	14.28%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5908      +/-   ##
==========================================
- Coverage   27.89%   27.88%   -0.02%     
==========================================
  Files         519      519              
  Lines       55926    55932       +6     
==========================================
- Hits        15603    15596       -7     
- Misses      39125    39136      +11     
- Partials     1198     1200       +2     

Flag	Coverage Δ
.	23.73% <25.00%> (-0.02%)	⬇️
.-pkg-app-pipedv1-plugin-example	0.00% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes	63.32% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	64.93% <ø> (ø)
.-pkg-app-pipedv1-plugin-wait	35.51% <ø> (ø)
.-pkg-plugin-sdk	49.33% <ø> (ø)
.-tool-actions-gh-release	19.23% <ø> (ø)
.-tool-actions-plan-preview	22.83% <ø> (ø)
.-tool-codegen-protoc-gen-auth	0.00% <ø> (ø)

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[ffjlabo]

Thank you