Add Repository.Log() method (fix #298)

- CommitIter is now an interface
- The old CommitIter implementation is now called StorerCommitIter
- CommitWalker and CommitWalkerPost are now iterators (CommitPreIterator and CommitPostIterator).
- Remove Commit.History() method. There are so many ways to iterate a commit history, depending of the use case. Now, instead of use the History() method, you must use CommitPreIterator or CommitPostIterator.
- Move commitSorterer to references.go because is the only place that it is used, and it must not be used into another place.
- Make References method private, it must only be used into blame logic.
- Added a TODO into references method, where the sortCommits is used to remove it in a near future.

1 files changed, 12 insertions, 11 deletions

diff --git a/plumbing/revlist/revlist.go b/plumbing/revlist/revlist.go
index eb9afaf..fbd1bd9 100644
--- a/plumbing/revlist/revlist.go
+++ b/plumbing/revlist/revlist.go
@@ -82,20 +82,21 @@ func reachableObjects(
 	commit *object.Commit,
 	seen map[plumbing.Hash]bool,
 	cb func(h plumbing.Hash)) error {
-	return object.WalkCommitHistory(commit, func(commit *object.Commit) error {
-		if seen[commit.Hash] {
-			return nil
-		}
+	return object.NewCommitPreIterator(commit).
+		ForEach(func(commit *object.Commit) error {
+			if seen[commit.Hash] {
+				return nil
+			}
 
-		cb(commit.Hash)
+			cb(commit.Hash)
 
-		tree, err := commit.Tree()
-		if err != nil {
-			return err
-		}
+			tree, err := commit.Tree()
+			if err != nil {
+				return err
+			}
 
-		return iterateCommitTrees(seen, tree, cb)
-	})
+			return iterateCommitTrees(seen, tree, cb)
+		})
 }
 
 // iterateCommitTrees iterate all reachable trees from the given commit