1 files changed, 110 insertions, 0 deletions
diff --git a/modules/git/commit_reader.go b/modules/git/commit_reader.go
new file mode 100644
index 00000000..8e2523d7
--- /dev/null
+++ b/modules/git/commit_reader.go
@@ -0,0 +1,110 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package git
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"strings"
+)
+
+// CommitFromReader will generate a Commit from a provided reader
+// We need this to interpret commits from cat-file or cat-file --batch
+//
+// If used as part of a cat-file --batch stream you need to limit the reader to the correct size
+func CommitFromReader(gitRepo *Repository, objectID ObjectID, reader io.Reader) (*Commit, error) {
+	commit := &Commit{
+		ID:        objectID,
+		Author:    &Signature{},
+		Committer: &Signature{},
+	}
+
+	payloadSB := new(strings.Builder)
+	signatureSB := new(strings.Builder)
+	messageSB := new(strings.Builder)
+	message := false
+	pgpsig := false
+
+	bufReader, ok := reader.(*bufio.Reader)
+	if !ok {
+		bufReader = bufio.NewReader(reader)
+	}
+
+readLoop:
+	for {
+		line, err := bufReader.ReadBytes('\n')
+		if err != nil {
+			if err == io.EOF {
+				if message {
+					_, _ = messageSB.Write(line)
+				}
+				_, _ = payloadSB.Write(line)
+				break readLoop
+			}
+			return nil, err
+		}
+		if pgpsig {
+			if len(line) > 0 && line[0] == ' ' {
+				_, _ = signatureSB.Write(line[1:])
+				continue
+			}
+			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, MustIDFromString(string(data)))
+				_, _ = payloadSB.Write(line)
+			case "parent":
+				commit.Parents = append(commit.Parents, MustIDFromString(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 "encoding":
+				_, _ = payloadSB.Write(line)
+			case "gpgsig":
+				fallthrough
+			case "gpgsig-sha256": // FIXME: no intertop, so only 1 exists at present.
+				_, _ = signatureSB.Write(data)
+				_ = signatureSB.WriteByte('\n')
+				pgpsig = true
+			}
+		} else {
+			_, _ = messageSB.Write(line)
+			_, _ = payloadSB.Write(line)
+		}
+	}
+	commit.CommitMessage = messageSB.String()
+	commit.Signature = &ObjectSignature{
+		Signature: signatureSB.String(),
+		Payload:   payloadSB.String(),
+	}
+	if len(commit.Signature.Signature) == 0 {
+		commit.Signature = nil
+	}
+
+	return commit, nil
+}