add comments on public methods

cmd/internal/depgraph/dependencygraph.go

@@ -23,36 +23,45 @@ import (
 	"gonum.org/v1/gonum/graph/simple"
 )
 
+// DependencyGraph represents dependencies between files in a Go package.
 type DependencyGraph struct {
 	*simple.DirectedGraph
 }
 
+// NewDependencyGraph returns an empty DependencyGraph.
 func NewDependencyGraph() *DependencyGraph {
 	return &DependencyGraph{DirectedGraph: simple.NewDirectedGraph()}
 }
 
+// NewNode returns a new Sourcefile node.
 func (g *DependencyGraph) NewNode() graph.Node {
 	return &Sourcefile{Node: g.DirectedGraph.NewNode()}
 }
 
+// Sourcefile represents a given source file in a Go package.
 type Sourcefile struct {
 	graph.Node
 	name string
 }
 
+// String returns the name attribute of Sourcefile.
 func (s *Sourcefile) String() string {
 	return s.name
 }
 
+// NewSourcefile returns a Sourcefile node with ID determined by the CRC32 hash
+// of the name of the source file.
 func NewSourcefile(name string) *Sourcefile {
 	hash := crc32.ChecksumIEEE([]byte(name))
 	return &Sourcefile{Node: simple.Node(hash), name: name}
 }
 
+// DOTID returns the name attribute of the source file.
 func (s *Sourcefile) DOTID() string {
 	return s.name
 }
 
+// SetDOTID sets the name attribute of a Sourcefile to the given id.
 func (s *Sourcefile) SetDOTID(id string) {
 	s.name = id
 }