render

type Params struct {
	// BackupDir is the directory where overwritten files will be backed up.
	// BackupDir is ignored if Backups is false.
	BackupDir string
	Backups   bool

	// If len(OverrideBuiltinVars)>0, then these values replace the normal
	// undercore-prefixed vars (_git_tag,  All map keys must begin with
	// underscore.
	OverrideBuiltinVars map[string]string

	// Fakeable time for testing.
	Clock clock.Clock

	// The fakeable working directory for testing.
	Cwd string

	// The value of --debug-scratch-contents.
	DebugScratchContents bool

	// The value of --debug-step-diffs.
	DebugStepDiffs bool

	// The directory that this operation is targeting, from the user's point of
	// view. It's sometimes the same as OutDir:
	//   - When Render() is being called as part of `abc render`,
	//     this is the same as OutDir.
	//   - When Render() is being called as part of `abc upgrade`,
	//     this is the directory that the template is installed to, and NOT the
	//     temp dir that receives the output of Render().
	//
	// This is optional. If unset, the value of OutDir will be used.
	DestDir string

	// The downloader that will provide the template.
	Downloader templatesource.Downloader

	// The value of --force-overwrite.
	ForceOverwrite bool

	// A fakeable filesystem for error injection in tests.
	FS common.FS

	// The value of --git-protocol.
	GitProtocol string

	// An optional extra directory that will be copied from in the case where an
	// "include" action has "from: destination". This is in addition to DestDir
	// above. The include action will copy from DestDir first and then from this
	// directory afterward, so files in this directory will take precedence.
	// Essentially, files in this dir are overlaid on top of other includes
	// files in an include-from-destination operation.
	IncludeFromDestExtraDir string

	// The value of --input-files.
	InputFiles []string

	// The value of --input, or another source of input values (e.g. the golden
	// test test.yaml).
	Inputs map[string]string

	// The value of --keep-temp-dirs.
	KeepTempDirs bool

	// The value of --manifest.
	Manifest bool

	// The directory where the rendered output will be written.
	OutDir string

	// Whether to prompt the user for inputs on stdin in the case where they're
	// not all provided in Inputs or InputFiles.
	Prompt bool
	// If Prompt is true, Prompter will be used if needed to ask the user for
	// any missing inputs. If Prompt is false, this is ignored.
	Prompter input.Prompter

	// The value of --skip-input-validation.
	SkipInputValidation bool

	// Normally, we'll only prompt if the input is a TTY. For testing, this
	// can be set to true to bypass the check and allow stdin to be something
	// other than a TTY, like an os.Pipe.
	SkipPromptTTYCheck bool

	// The location from which the template is installed, as provided by the
	// user on the command line, or from the manifest. This is only used in
	// log messages and for the _flag_source variable in print actions.
	SourceForMessages string

	// The output stream used by "print" actions.
	Stdout io.Writer

	// The directory under which to create temp directories. Normally empty,
	// except in testing.
	TempDirBase string
}

type Result struct {
	// IncludedFromDestination is a set of files that were the subject of an
	// "include" action that had "from: destination". This exists primarily for
	// the sake of the "upgrade" command, which needs to know this. Other
	// callers should not use this field.
	IncludedFromDestination []string

	// ManifestPath, if set, is the relative path to the manifest file, starting
	// from the destination directory (e.g. ".abc/manifest_123.yaml"). If
	// manifest output wasn't enabled (see the --manifest flag), then this will
	// be empty.
	ManifestPath string
}