1 files changed, 78 insertions, 0 deletions
diff --git a/modules/git/parse.go b/modules/git/parse.go
new file mode 100644
index 0000000000..eb26632cc0
--- /dev/null
+++ b/modules/git/parse.go
@@ -0,0 +1,78 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package git
+
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"code.gitea.io/gitea/modules/optional"
+)
+
+var sepSpace = []byte{' '}
+
+type LsTreeEntry struct {
+	ID        ObjectID
+	EntryMode EntryMode
+	Name      string
+	Size      optional.Option[int64]
+}
+
+func parseLsTreeLine(line []byte) (*LsTreeEntry, error) {
+	// expect line to be of the form:
+	// <mode> <type> <sha> <space-padded-size>\t<filename>
+	// <mode> <type> <sha>\t<filename>
+
+	var err error
+	posTab := bytes.IndexByte(line, '\t')
+	if posTab == -1 {
+		return nil, fmt.Errorf("invalid ls-tree output (no tab): %q", line)
+	}
+
+	entry := new(LsTreeEntry)
+
+	entryAttrs := line[:posTab]
+	entryName := line[posTab+1:]
+
+	entryMode, entryAttrs, _ := bytes.Cut(entryAttrs, sepSpace)
+	_ /* entryType */, entryAttrs, _ = bytes.Cut(entryAttrs, sepSpace) // the type is not used, the mode is enough to determine the type
+	entryObjectID, entryAttrs, _ := bytes.Cut(entryAttrs, sepSpace)
+	if len(entryAttrs) > 0 {
+		entrySize := entryAttrs // the last field is the space-padded-size
+		size, _ := strconv.ParseInt(strings.TrimSpace(string(entrySize)), 10, 64)
+		entry.Size = optional.Some(size)
+	}
+
+	switch string(entryMode) {
+	case "100644":
+		entry.EntryMode = EntryModeBlob
+	case "100755":
+		entry.EntryMode = EntryModeExec
+	case "120000":
+		entry.EntryMode = EntryModeSymlink
+	case "160000":
+		entry.EntryMode = EntryModeCommit
+	case "040000", "040755": // git uses 040000 for tree object, but some users may get 040755 for unknown reasons
+		entry.EntryMode = EntryModeTree
+	default:
+		return nil, fmt.Errorf("unknown type: %v", string(entryMode))
+	}
+
+	entry.ID, err = NewIDFromString(string(entryObjectID))
+	if err != nil {
+		return nil, fmt.Errorf("invalid ls-tree output (invalid object id): %q, err: %w", line, err)
+	}
+
+	if len(entryName) > 0 && entryName[0] == '"' {
+		entry.Name, err = strconv.Unquote(string(entryName))
+		if err != nil {
+			return nil, fmt.Errorf("invalid ls-tree output (invalid name): %q, err: %w", line, err)
+		}
+	} else {
+		entry.Name = string(entryName)
+	}
+	return entry, nil
+}