1 files changed, 108 insertions, 0 deletions
diff --git a/modules/git/commit_reader.go b/modules/git/commit_reader.go
new file mode 100644
index 0000000000..06d8f426d7
--- /dev/null
+++ b/modules/git/commit_reader.go
@@ -0,0 +1,108 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package git
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+// CommitFromReader will generate a Commit from a provided reader
+// We will need this to interpret commits from cat-file
+func CommitFromReader(gitRepo *Repository, sha plumbing.Hash, reader io.Reader) (*Commit, error) {
+	commit := &Commit{
+		ID: sha,
+	}
+
+	payloadSB := new(strings.Builder)
+	signatureSB := new(strings.Builder)
+	messageSB := new(strings.Builder)
+	message := false
+	pgpsig := false
+
+	scanner := bufio.NewScanner(reader)
+	// Split by '\n' but include the '\n'
+	scanner.Split(func(data []byte, atEOF bool) (advance int, token []byte, err error) {
+		if atEOF && len(data) == 0 {
+			return 0, nil, nil
+		}
+		if i := bytes.IndexByte(data, '\n'); i >= 0 {
+			// We have a full newline-terminated line.
+			return i + 1, data[0 : i+1], nil
+		}
+		// If we're at EOF, we have a final, non-terminated line. Return it.
+		if atEOF {
+			return len(data), data, nil
+		}
+		// Request more data.
+		return 0, nil, nil
+	})
+
+	for scanner.Scan() {
+		line := scanner.Bytes()
+		if pgpsig {
+			if len(line) > 0 && line[0] == ' ' {
+				_, _ = signatureSB.Write(line[1:])
+				continue
+			} else {
+				pgpsig = false
+			}
+		}
+
+		if !message {
+			// This is probably not correct but is copied from go-gits interpretation...
+			trimmed := bytes.TrimSpace(line)
+			if len(trimmed) == 0 {
+				message = true
+				_, _ = payloadSB.Write(line)
+				continue
+			}
+
+			split := bytes.SplitN(trimmed, []byte{' '}, 2)
+			var data []byte
+			if len(split) > 1 {
+				data = split[1]
+			}
+
+			switch string(split[0]) {
+			case "tree":
+				commit.Tree = *NewTree(gitRepo, plumbing.NewHash(string(data)))
+				_, _ = payloadSB.Write(line)
+			case "parent":
+				commit.Parents = append(commit.Parents, plumbing.NewHash(string(data)))
+				_, _ = payloadSB.Write(line)
+			case "author":
+				commit.Author = &Signature{}
+				commit.Author.Decode(data)
+				_, _ = payloadSB.Write(line)
+			case "committer":
+				commit.Committer = &Signature{}
+				commit.Committer.Decode(data)
+				_, _ = payloadSB.Write(line)
+			case "gpgsig":
+				_, _ = signatureSB.Write(data)
+				_ = signatureSB.WriteByte('\n')
+				pgpsig = true
+			}
+		} else {
+			_, _ = messageSB.Write(line)
+		}
+	}
+	commit.CommitMessage = messageSB.String()
+	_, _ = payloadSB.WriteString(commit.CommitMessage)
+	commit.Signature = &CommitGPGSignature{
+		Signature: signatureSB.String(),
+		Payload:   payloadSB.String(),
+	}
+	if len(commit.Signature.Signature) == 0 {
+		commit.Signature = nil
+	}
+
+	return commit, scanner.Err()
+}