Initial implementation using libgit2

Closes #1 (closed)

git/git2go.go

+package git
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+
+	"gopkg.in/libgit2/git2go.v25"
+)
+
+var (
+	ZeroHash                 = &git.Oid{}
+	submoduleFilemode uint16 = 0160000
+)
+
+type git2GoRepository struct {
+	Repository *git.Repository
+
+	FromHash *git.Oid
+	ToHash   *git.Oid
+
+	FromCommit *git.Commit
+	ToCommit   *git.Commit
+}
+
+func NewGit2GoRepository(projectPath string, fromSHA string, toSHA string) (*git2GoRepository, error) {
+	out := &git2GoRepository{}
+
+	repo, err := git.OpenRepository(projectPath)
+	if err != nil {
+		return nil, err
+	}
+	out.Repository = repo
+
+	if fromSHA == "" {
+		out.FromHash = ZeroHash
+	} else {
+		oid, err := git.NewOid(fromSHA)
+		if err != nil {
+			return nil, err
+		}
+		out.FromHash = oid
+
+		commit, err := out.Repository.LookupCommit(out.FromHash)
+		if err != nil {
+			return nil, fmt.Errorf("Bad from SHA (%s): %s", out.FromHash, err)
+		}
+
+		out.FromCommit = commit
+	}
+
+	if toSHA == "" {
+		ref, err := out.Repository.Head()
+		if err != nil {
+			return nil, err
+		}
+
+		out.ToHash = ref.Target()
+	} else {
+		oid, err := git.NewOid(toSHA)
+		if err != nil {
+			return nil, err
+		}
+
+		out.ToHash = oid
+	}
+
+	commit, err := out.Repository.LookupCommit(out.ToHash)
+	if err != nil {
+		return nil, fmt.Errorf("Bad to SHA (%s): %s", out.ToHash, err)
+	}
+
+	out.ToCommit = commit
+
+	return out, nil
+}
+
+func (r *git2GoRepository) diff() (*git.Diff, error) {
+	var fromTree, toTree *git.Tree
+
+	if r.FromCommit != nil {
+		tree, err := r.FromCommit.Tree()
+		if err != nil {
+			return nil, err
+		}
+
+		fromTree = tree
+	}
+
+	toTree, err := r.ToCommit.Tree()
+	if err != nil {
+		return nil, err
+	}
+
+	defOpts, err := git.DefaultDiffOptions()
+	if err != nil {
+		return nil, err
+	}
+
+	opts := &defOpts
+	opts.IgnoreSubmodules = git.SubmoduleIgnoreAll
+	opts.Flags = defOpts.Flags | git.DiffIgnoreSubmodules
+
+	return r.Repository.DiffTreeToTree(fromTree, toTree, opts)
+}
+
+func git2GoBuildSignature(sig *git.Signature) Signature {
+	return Signature{
+		Name:  sig.Name,
+		Email: sig.Email,
+		When:  sig.When,
+	}
+}
+
+func (r *git2GoRepository) callout(file git.DiffFile, next FileFunc) error {
+	blob, err := r.Repository.LookupBlob(file.Oid)
+	if err != nil {
+		return err
+	}
+
+	f := &File{
+		Path: file.Path,
+		Oid:  file.Oid.String(),
+		Blob: func() (io.ReadCloser, error) {
+			return ioutil.NopCloser(bytes.NewReader(blob.Contents())), nil
+		},
+		Size: blob.Size(),
+	}
+
+	return next(f, r.FromHash.String(), r.ToHash.String())
+}
+
+func (r *git2GoRepository) EachFileChange(ins, mod, del FileFunc) error {
+	diff, err := r.diff()
+	if err != nil {
+		return err
+	}
+
+	numDeltas, err := diff.NumDeltas()
+	if err != nil {
+		return err
+	}
+
+	for i := 0; i < numDeltas; i++ {
+		delta, err := diff.GetDelta(i)
+		if err != nil {
+			return err
+		}
+
+		if delta.OldFile.Mode == submoduleFilemode {
+			continue
+		}
+
+		if delta.NewFile.Mode == submoduleFilemode {
+			continue
+		}
+
+		switch delta.Status {
+		case git.DeltaAdded, git.DeltaCopied:
+			err = r.callout(delta.NewFile, ins)
+		case git.DeltaModified:
+			err = r.callout(delta.NewFile, mod)
+		case git.DeltaDeleted:
+			err = r.callout(delta.OldFile, del)
+		case git.DeltaRenamed:
+			err = r.callout(delta.OldFile, del)
+			if err == nil {
+				err = r.callout(delta.NewFile, ins)
+			}
+		default:
+			err = fmt.Errorf("Unrecognised change calculating diff: %+v", delta)
+		}
+
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (r *git2GoRepository) EachCommit(f CommitFunc) error {
+	rev, err := r.Repository.Walk()
+	if err != nil {
+		return err
+	}
+	//	defer rev.Free()
+
+	if err := rev.Push(r.ToHash); err != nil {
+		return err
+	}
+
+	var outErr error
+	iterator := func(c *git.Commit) bool {
+		commit := &Commit{
+			Message:   c.Message(),
+			Hash:      c.Id().String(),
+			Author:    git2GoBuildSignature(c.Author()),
+			Committer: git2GoBuildSignature(c.Committer()),
+		}
+
+		// abort walking due to reaching the termination point
+		if c.Id().Equal(r.FromHash) {
+			return false
+		}
+
+		outErr = f(commit)
+
+		// Abort walking due to an error
+		if outErr != nil {
+			return false
+		}
+
+		return true
+	}
+
+	if err := rev.Iterate(iterator); err != nil {
+		return fmt.Errorf("WalkCommitHistory: %s", err)
+	}
+
+	return outErr
+}