refactor: Make output for cmd help, adhoc data more consistent

Usage funcs in pkg cmd would write some stuff to stdout, some to stderr.
Make this consistent. Going with stdout for usage funcs to make it
easier to capture help in a file.

Specifying outputs in the library code helps make the Info subcommand
cleaner. If you've selected the json format output, you're piping to jq
and there's an error, then invalid json is written to stdout. So, write
that adhoc stuff to stderr.

godfish.go

@@ -186,7 +186,7 @@ func runMigration(driver Driver, pathToFile string, mig internal.Migration) (err
 	if mig.Indirection().Value == internal.DirReverse {
 		gerund = "rolling back"
 	}
-	fmt.Printf("%s version %q ... ", gerund, mig.Version().String())
+	fmt.Fprintf(os.Stderr, "%s version %q ... ", gerund, mig.Version().String())
 
 	if err = driver.Execute(string(data)); err != nil {
 		err = &runMigrationError{
@@ -204,7 +204,7 @@ func runMigration(driver Driver, pathToFile string, mig internal.Migration) (err
 		mig.Version().String(),
 	)
 	if err == nil {
-		fmt.Println("ok")
+		fmt.Fprintln(os.Stderr, "ok")
 	}
 	return
 }
@@ -252,7 +252,7 @@ func choosePrinter(format string, w io.Writer) (out internal.InfoPrinter) {
 func Init(pathToFile string) (err error) {
 	_, err = os.Stat(pathToFile)
 	if err == nil {
-		fmt.Printf("config file %q already present\n", pathToFile)
+		fmt.Fprintf(os.Stderr, "config file %q already present\n", pathToFile)
 		return nil
 	}
 	if !os.IsNotExist(err) {
@@ -363,7 +363,7 @@ func (m *migrationFinder) available() (out []internal.Migration, err error) {
 	for _, fn := range filenames {
 		mig, ierr := internal.ParseMigration(internal.Filename(fn))
 		if errors.Is(ierr, internal.ErrDataInvalid) {
-			fmt.Println(ierr)
+			fmt.Fprintln(os.Stderr, ierr)
 			continue
 		} else if ierr != nil {
 			err = ierr

internal/cmd/cmd.go

@@ -50,7 +50,7 @@ func New(driver godfish.Driver) Root {
 		},
 	}
 
-	rootFlags := flag.NewFlagSet("godfish", flag.ExitOnError)
+	rootFlags := newFlagSet("godfish")
 	rootFlags.Usage = func() {
 		fmt.Fprintf(rootFlags.Output(), `Usage:
 
@@ -124,9 +124,15 @@ Examples:
 	}
 }
 
+func newFlagSet(name string) (out *flag.FlagSet) {
+	out = flag.NewFlagSet(name, flag.ExitOnError)
+	out.SetOutput(os.Stdout)
+	return
+}
+
 // printFlagDefaults calls PrintDefaults on f. It helps make help message
 // formatting more consistent.
 func printFlagDefaults(f *flag.FlagSet) {
-	fmt.Printf("\n%s flags:\n\n", f.Name())
+	fmt.Fprintf(f.Output(), "\n%s flags:\n\n", f.Name())
 	f.PrintDefaults()
 }

internal/cmd/create-migration.go

@@ -18,7 +18,7 @@ func makeCreateMigration(subcmdName string) alf.Directive {
 
 	// Other subcommands scope the flagset within the Setup func. However, this
 	// one is scoped up here to check if some flags were specified at runtime.
-	flags := flag.NewFlagSet(subcmdName, flag.ExitOnError)
+	flags := newFlagSet(subcmdName)
 
 	return &alf.Command{
 		Description: "generate migration files",
@@ -48,7 +48,7 @@ func makeCreateMigration(subcmdName string) alf.Directive {
 				"customize the directional part of the filename for reverse migration",
 			)
 			flags.Usage = func() {
-				fmt.Printf(`Usage: %s [godfish-flags] %s [%s-flags]
+				fmt.Fprintf(flags.Output(), `Usage: %s [godfish-flags] %s [%s-flags]
 
 	Generate migration files: one meant for the "forward" direction,
 	another meant for "reverse". Optionally create a migration in the forward

internal/cmd/info.go

@@ -18,7 +18,7 @@ func makeInfo(name string) alf.Directive {
 	return &alf.Command{
 		Description: "output applied migrations, migrations to apply",
 		Setup: func(p flag.FlagSet) *flag.FlagSet {
-			flags := flag.NewFlagSet(name, flag.ExitOnError)
+			flags := newFlagSet(name)
 			flags.StringVar(
 				&direction,
 				"direction",
@@ -38,7 +38,7 @@ func makeInfo(name string) alf.Directive {
 				fmt.Sprintf("timestamp of migration, format: %s", internal.TimeFormat),
 			)
 			flags.Usage = func() {
-				fmt.Printf(`Usage: %s [godfish-flags] %s [%s-flags]
+				fmt.Fprintf(flags.Output(), `Usage: %s [godfish-flags] %s [%s-flags]
 
 	List applied migrations, preview migrations to apply.
 

internal/cmd/init.go

@@ -15,15 +15,15 @@ func makeInit(name string) alf.Directive {
 	return &alf.Command{
 		Description: "create godfish configuration file",
 		Setup: func(p flag.FlagSet) *flag.FlagSet {
-			flags := flag.NewFlagSet(name, flag.ExitOnError)
+			flags := newFlagSet(name)
 			flags.StringVar(
 				&conf,
 				"conf",
 				".godfish.json",
 				"path to godfish config file",
 			)
 			flags.Usage = func() {
-				fmt.Printf(`Usage: %s [godfish-flags] %s [%s-flags]
+				fmt.Fprintf(flags.Output(), `Usage: %s [godfish-flags] %s [%s-flags]
 
 	Creates a configuration file, unless it already exists.
 `,

internal/cmd/migrate.go

@@ -16,15 +16,15 @@ func makeMigrate(name string) alf.Directive {
 	return &alf.Command{
 		Description: "execute migration(s) in the forward direction",
 		Setup: func(p flag.FlagSet) *flag.FlagSet {
-			flags := flag.NewFlagSet(name, flag.ExitOnError)
+			flags := newFlagSet(name)
 			flags.StringVar(
 				&version,
 				"version",
 				"",
 				fmt.Sprintf("timestamp of migration, format: %s", internal.TimeFormat),
 			)
 			flags.Usage = func() {
-				fmt.Printf(`Usage: %s [godfish-flags] %s [%s-flags]
+				fmt.Fprintf(flags.Output(), `Usage: %s [godfish-flags] %s [%s-flags]
 
 	Execute migration(s) in the forward direction. If the "version" is left
 	unspecified, then all available migrations are executed. Otherwise,
@@ -57,9 +57,9 @@ func makeRemigrate(name string) alf.Directive {
 	return &alf.Command{
 		Description: "rollback and then re-apply the last migration",
 		Setup: func(p flag.FlagSet) *flag.FlagSet {
-			flags := flag.NewFlagSet(name, flag.ExitOnError)
+			flags := newFlagSet(name)
 			flags.Usage = func() {
-				fmt.Printf(`Usage: %s [godfish-flags] %s [%s-flags]
+				fmt.Fprintf(flags.Output(), `Usage: %s [godfish-flags] %s [%s-flags]
 
 	Execute the last migration in reverse (rollback) and then execute the same
 	one forward. This could be useful for development.
@@ -89,15 +89,15 @@ func makeRollback(name string) alf.Directive {
 	return &alf.Command{
 		Description: "execute migration(s) in the reverse direction",
 		Setup: func(p flag.FlagSet) *flag.FlagSet {
-			flags := flag.NewFlagSet(name, flag.ExitOnError)
+			flags := newFlagSet(name)
 			flags.StringVar(
 				&version,
 				"version",
 				"",
 				fmt.Sprintf("timestamp of migration, format: %s", internal.TimeFormat),
 			)
 			flags.Usage = func() {
-				fmt.Printf(`Usage: %s [godfish-flags] %s [%s-flags]
+				fmt.Fprintf(flags.Output(), `Usage: %s [godfish-flags] %s [%s-flags]
 
 	Execute migration(s) in the reverse direction. If the "version" is left
 	unspecified, then only the first available migration is executed. Otherwise,

internal/cmd/version.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
+	"os"
 
 	"github.com/rafaelespinoza/alf"
 )
@@ -26,10 +27,10 @@ func makeVersion(name string) alf.Directive {
 	return &alf.Command{
 		Description: "show metadata about the build",
 		Setup: func(p flag.FlagSet) *flag.FlagSet {
-			flags := flag.NewFlagSet(name, flag.ExitOnError)
+			flags := newFlagSet(name)
 			flags.BoolVar(&formatJSON, "json", false, "format output as JSON")
 			flags.Usage = func() {
-				fmt.Printf(`Usage: %s [flags]
+				fmt.Fprintf(flags.Output(), `Usage: %s [flags]
 
 	Prints some versioning info to stdout. Pass the -json flag to get JSON.
 `,
@@ -40,13 +41,16 @@ func makeVersion(name string) alf.Directive {
 			return flags
 		},
 		Run: func(_ context.Context) error {
+			// Calling fmt.Print* also writes to stdout, but want to be explicit
+			// about where this subcommand output goes.
+			w := os.Stdout
 			if !formatJSON {
-				fmt.Printf("BranchName:	%s\n", versionBranchName)
-				fmt.Printf("BuildTime: 	%s\n", versionBuildTime)
-				fmt.Printf("Driver: 	%s\n", versionDriver)
-				fmt.Printf("CommitHash:	%s\n", versionCommitHash)
-				fmt.Printf("GoVersion: 	%s\n", versionGoVersion)
-				fmt.Printf("Tag:		%s\n", versionTag)
+				fmt.Fprintf(w, "BranchName:	%s\n", versionBranchName)
+				fmt.Fprintf(w, "BuildTime: 	%s\n", versionBuildTime)
+				fmt.Fprintf(w, "Driver: 	%s\n", versionDriver)
+				fmt.Fprintf(w, "CommitHash:	%s\n", versionCommitHash)
+				fmt.Fprintf(w, "GoVersion: 	%s\n", versionGoVersion)
+				fmt.Fprintf(w, "Tag:		%s\n", versionTag)
 				return nil
 			}
 			out, err := json.Marshal(
@@ -62,7 +66,7 @@ func makeVersion(name string) alf.Directive {
 			if err != nil {
 				return err
 			}
-			fmt.Printf("%s\n", out)
+			fmt.Fprintf(w, "%s\n", out)
 			return nil
 		},
 	}

internal/migration.go

@@ -118,18 +118,18 @@ func (m *MigrationParams) GenerateFiles() (err error) {
 	if forwardFile, err = newMigrationFile(m.Forward, m.Dirpath); err != nil {
 		return
 	}
-	fmt.Println("created forward file:", forwardFile.Name())
+	fmt.Fprintln(os.Stderr, "created forward file:", forwardFile.Name())
 	defer forwardFile.Close()
 
 	if !m.Reversible {
-		fmt.Println("migration marked irreversible, did not create reverse file")
+		fmt.Fprintln(os.Stderr, "migration marked irreversible, did not create reverse file")
 		return
 	}
 
 	if reverseFile, err = newMigrationFile(m.Reverse, m.Dirpath); err != nil {
 		return
 	}
-	fmt.Println("created reverse file:", reverseFile.Name())
+	fmt.Fprintln(os.Stderr, "created reverse file:", reverseFile.Name())
 	defer reverseFile.Close()
 	return
 }