Update comments

Signed-off-by: Filip Navara <filip.navara@gmail.com>

Author: filipnavara

plumbing/object/commitnode.go

@@ -8,8 +8,8 @@ import (
 	"gopkg.in/src-d/go-git.v4/plumbing/storer"
 )
 
-// CommitNode is generic interface encapsulating either Commit object or
-// graphCommitNode object
+// CommitNode is generic interface encapsulating a lightweight commit object retrieved
+// from CommitNodeIndex
 type CommitNode interface {
 	// ID returns the Commit object id referenced by the commit graph node.
 	ID() plumbing.Hash
@@ -30,7 +30,6 @@ type CommitNode interface {
 }
 
 // CommitNodeIndex is generic interface encapsulating an index of CommitNode objects
-// and accessor methods for walking it as a directed graph
 type CommitNodeIndex interface {
 	// Get returns a commit node from a commit hash
 	Get(hash plumbing.Hash) (CommitNode, error)

plumbing/object/commitnode_graph.go

@@ -33,6 +33,8 @@ type graphCommitNodeIndex struct {
 	s           storer.EncodedObjectStorer
 }
 
+// NewGraphCommitNodeIndex returns CommitNodeIndex implementation that uses commit-graph
+// files as backing storage and falls back to object storage when necessary
 func NewGraphCommitNodeIndex(commitGraph commitgraph.Index, s storer.EncodedObjectStorer) CommitNodeIndex {
 	return &graphCommitNodeIndex{commitGraph, s}
 }

plumbing/object/commitnode_object.go

@@ -15,6 +15,8 @@ type objectCommitNode struct {
 	commit    *Commit
 }
 
+// NewObjectCommitNodeIndex returns CommitNodeIndex implementation that uses
+// only object storage to load the nodes
 func NewObjectCommitNodeIndex(s storer.EncodedObjectStorer) CommitNodeIndex {
 	return &objectCommitNodeIndex{s}
 }