Fix issues with walking commit graph across merges.

Signed-off-by: Filip Navara <[email protected]>

Author: filipnavara

modules/git/commit.go

@@ -14,6 +14,8 @@ import (
 	"net/http"
 	"strconv"
 	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/object"
 )
 
 // Commit represents a git commit.
@@ -52,6 +54,61 @@ func newGPGSignatureFromCommitline(data []byte, signatureStart int, tag bool) (*
 	return sig, nil
 }
 
+func convertPGPSignature(c *object.Commit) *CommitGPGSignature {
+	if c.PGPSignature == "" {
+		return nil
+	}
+
+	var w strings.Builder
+	var err error
+
+	if _, err = fmt.Fprintf(&w, "tree %s\n", c.TreeHash.String()); err != nil {
+		return nil
+	}
+
+	for _, parent := range c.ParentHashes {
+		if _, err = fmt.Fprintf(&w, "parent %s\n", parent.String()); err != nil {
+			return nil
+		}
+	}
+
+	if _, err = fmt.Fprint(&w, "author "); err != nil {
+		return nil
+	}
+
+	if err = c.Author.Encode(&w); err != nil {
+		return nil
+	}
+
+	if _, err = fmt.Fprint(&w, "\ncommitter "); err != nil {
+		return nil
+	}
+
+	if err = c.Committer.Encode(&w); err != nil {
+		return nil
+	}
+
+	if _, err = fmt.Fprintf(&w, "\n\n%s", c.Message); err != nil {
+		return nil
+	}
+
+	return &CommitGPGSignature{
+		Signature: c.PGPSignature,
+		Payload:   w.String(),
+	}
+}
+
+func convertCommit(c *object.Commit) *Commit {
+	return &Commit{
+		ID:            c.Hash,
+		CommitMessage: c.Message,
+		Committer:     &c.Committer,
+		Author:        &c.Author,
+		Signature:     convertPGPSignature(c),
+		parents:       c.ParentHashes,
+	}
+}
+
 // Message returns the commit message. Same as retrieving CommitMessage directly.
 func (c *Commit) Message() string {
 	return c.CommitMessage