Add support for incremental stamping

[randrei-adobe]

Description

Modify the create_gitops_pr utility to optionally implement the following algorithm:

• Assume the service.yaml file is an output of the service.gitops target
• Run service.gitops > service.yaml
• Calculate service.yaml digest > service.yaml.digest
• Check if the contents of the service.yaml.digest are the same as those committed into git
  • Stop if there are no changes to the service.yaml.digest file
• Stamp (replace placeholders) service.yaml
• Commit and push the changes to service.yaml.digest and service.yaml

Related Issue

Motivation and Context

The existing GitOps PR process creates a new GitOps PR when a ConfigMap object that exposes a volatile file changes even if the deployment artifact doesn't change.

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[kzadorozhny]

We should not do stamping of stamps in .show and .apply commands.

1. The git command will not work because the current directory is not the source directory.
2. We will be breaking the idempotency properties of .show and apply commands, which is no backward compatible behavior change.

[kzadorozhny]

Suggested change

	dryRun = flag.Bool("dry_run", false, "Do not create PRs, just print what would be done")
	stamp = flag.Bool("stamp", false, "Stamp results of gitops targets with volatile information")
	stamp = flag.Bool("stamp", false, "Stamp results of gitops targets with volatile information")
	dryRun = flag.Bool("dry_run", false, "Do not create PRs, just print what would be done")

Historically we kept dryRun as a last argument definition.

[kzadorozhny]

This function doesn't seem to belong to the public interface of git module. Please make it private or inline.

[kzadorozhny]

I'd prefer the use of the Scanner. While it will be more verbose it will be more obvious what empty lines re not returned.

    var files []string
    sc := bufio.NewScanner(strings.NewReader(s))
    for sc.Scan() {
        files = append(files, sc.Text())
    }
    return lines

[kzadorozhny]

Suggested change

	func (r *Repo) RemoveDiff(fileName string) {
	func (r *Repo) RestoreFile(fileName string) {

Align with the terminology used by Git. For example:

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
	modified:   src/index.ts

[kzadorozhny]

Suggested change

	func getContext(workdir *git.Repo, branchName string) map[string]interface{} {
	func getGitStatusDict(workdir *git.Repo, branchName string) map[string]interface{} {

getContext is too generic.

[kzadorozhny]

fasttemplate.Execute function writes directly into file.

Suggested change

	stampedTemplate := fasttemplate.ExecuteString(string(template), "{{", "}}", ctx)
	outf, err = os.OpenFile(fullPath, os.O_RDWR|os.O_CREATE|os.O_TRUNC, perm)
	if err != nil {
	log.Fatalf("Unable to create output file %s: %v", output, err)
	}
	defer outf.Close()
	_, err = fasttemplate.Execute(string(template), "{{", "}}", ctx)