Add godoc strings to all exported types, functions, and fields

Documents:
- cli: NO_COLOR, RunOptions fields, CLIApp, VersionString
- checker: Result fields, Status constants, CheckStatus fields
- scanner: EnumerateStatus, ScanStatus, Options, FileEntry fields
- log: Level alias, DisableStyling, Init, Info/Debug functions,
  verbosity helpers, GetLogger, GetLevel, WithError
- mfer: ManifestScanOptions, New, NewFromPaths, NewFromFS, MAGIC

mfer/manifest.go

@@ -39,9 +39,10 @@ func (m *manifest) String() string {
 	return fmt.Sprintf("<Manifest count=%d totalSize=%d>", len(m.files), m.totalFileSize)
 }
 
+// ManifestScanOptions configures behavior when scanning directories for manifest generation.
 type ManifestScanOptions struct {
-	IgnoreDotfiles bool
-	FollowSymLinks bool
+	IgnoreDotfiles bool // Skip files and directories starting with a dot
+	FollowSymLinks bool // Resolve symlinks instead of skipping them
 }
 
 func (m *manifest) HasError() bool {
@@ -77,11 +78,13 @@ func (m *manifest) addInputFS(f afero.Fs) error {
 	return nil
 }
 
+// New creates an empty manifest.
 func New() *manifest {
 	m := &manifest{}
 	return m
 }
 
+// NewFromPaths creates a manifest configured to scan the given filesystem paths.
 func NewFromPaths(options *ManifestScanOptions, inputPaths ...string) (*manifest, error) {
 	log.Dump(inputPaths)
 	m := New()
@@ -95,6 +98,7 @@ func NewFromPaths(options *ManifestScanOptions, inputPaths ...string) (*manifest
 	return m, nil
 }
 
+// NewFromFS creates a manifest configured to scan the given afero filesystem.
 func NewFromFS(options *ManifestScanOptions, fs afero.Fs) (*manifest, error) {
 	m := New()
 	m.scanOptions = options

mfer/serialize.go

@@ -10,9 +10,7 @@ import (
 	"google.golang.org/protobuf/proto"
 )
 
-// was go-generate protoc --go_out=. --go_opt=paths=source_relative mf.proto
-
-// rot13("MANIFEST")
+// MAGIC is the file format magic bytes prefix (rot13 of "MANIFEST").
 const MAGIC string = "ZNAVSRFG"
 
 func newTimestampFromTime(t time.Time) *Timestamp {