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, 45 insertions, 26 deletions

diff --git a/repository.go b/repository.go
index 9e325e4..d9a1d7e 100644
--- a/repository.go
+++ b/repository.go
@@ -608,6 +608,26 @@ func (r *Repository) Push(o *PushOptions) error {
 	return remote.Push(o)
 }
 
+// Log returns the commit history from the given LogOptions.
+func (r *Repository) Log(o *LogOptions) (object.CommitIter, error) {
+	h := o.From
+	if o.From == plumbing.ZeroHash {
+		head, err := r.Head()
+		if err != nil {
+			return nil, err
+		}
+
+		h = head.Hash()
+	}
+
+	commit, err := r.CommitObject(h)
+	if err != nil {
+		return nil, err
+	}
+
+	return object.NewCommitPreIterator(commit), nil
+}
+
 // Tags returns all the References from Tags. This method returns all the tag
 // types, lightweight, and annotated ones.
 func (r *Repository) Tags() (storer.ReferenceIter, error) {
@@ -671,7 +691,7 @@ func (r *Repository) CommitObject(h plumbing.Hash) (*object.Commit, error) {
 }
 
 // CommitObjects returns an unsorted CommitIter with all the commits in the repository.
-func (r *Repository) CommitObjects() (*object.CommitIter, error) {
+func (r *Repository) CommitObjects() (object.CommitIter, error) {
 	iter, err := r.Storer.IterEncodedObjects(plumbing.CommitObject)
 	if err != nil {
 		return nil, err
@@ -838,29 +858,28 @@ func (r *Repository) ResolveRevision(rev plumbing.Revision) (*plumbing.Hash, err
 				commit = c
 			}
 		case revision.CaretReg:
-			history, err := commit.History()
-
-			if err != nil {
-				return &plumbing.ZeroHash, err
-			}
+			history := object.NewCommitPreIterator(commit)
 
 			re := item.(revision.CaretReg).Regexp
 			negate := item.(revision.CaretReg).Negate
 
 			var c *object.Commit
 
-			for i := 0; i < len(history); i++ {
-				if !negate && re.MatchString(history[i].Message) {
-					c = history[i]
-
-					break
+			err := history.ForEach(func(hc *object.Commit) error {
+				if !negate && re.MatchString(hc.Message) {
+					c = hc
+					return storer.ErrStop
 				}
 
-				if negate && !re.MatchString(history[i].Message) {
-					c = history[i]
-
-					break
+				if negate && !re.MatchString(hc.Message) {
+					c = hc
+					return storer.ErrStop
 				}
+
+				return nil
+			})
+			if err != nil {
+				return &plumbing.ZeroHash, err
 			}
 
 			if c == nil {
@@ -869,21 +888,21 @@ func (r *Repository) ResolveRevision(rev plumbing.Revision) (*plumbing.Hash, err
 
 			commit = c
 		case revision.AtDate:
-			history, err := commit.History()
-
-			if err != nil {
-				return &plumbing.ZeroHash, err
-			}
+			history := object.NewCommitPreIterator(commit)
 
 			date := item.(revision.AtDate).Date
-			var c *object.Commit
 
-			for i := 0; i < len(history); i++ {
-				if date.Equal(history[i].Committer.When.UTC()) || history[i].Committer.When.UTC().Before(date) {
-					c = history[i]
-
-					break
+			var c *object.Commit
+			err := history.ForEach(func(hc *object.Commit) error {
+				if date.Equal(hc.Committer.When.UTC()) || hc.Committer.When.UTC().Before(date) {
+					c = hc
+					return storer.ErrStop
 				}
+
+				return nil
+			})
+			if err != nil {
+				return &plumbing.ZeroHash, err
 			}
 
 			if c == nil {