Use git log name-status in get last commit (#16059)

* Improve get last commit using git log --name-status

git log --name-status -c provides information about the diff between a
commit and its parents. Using this and adjusting the algorithm to use
the first change to a path allows for a much faster generation of commit
info.

There is a subtle change in the results generated but this will cause
the results to more closely match those from elsewhere.

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/github.com/djherbis/buffer/file.go

@@ -0,0 +1,72 @@
+package buffer
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/djherbis/buffer/wrapio"
+)
+
+// File is used as the backing resource for a the NewFile BufferAt.
+type File interface {
+	Name() string
+	Stat() (fi os.FileInfo, err error)
+	io.ReaderAt
+	io.WriterAt
+	Close() error
+}
+
+type fileBuffer struct {
+	file File
+	*wrapio.Wrapper
+}
+
+// NewFile returns a new BufferAt backed by "file" with max-size N.
+func NewFile(N int64, file File) BufferAt {
+	return &fileBuffer{
+		file:    file,
+		Wrapper: wrapio.NewWrapper(file, 0, 0, N),
+	}
+}
+
+func init() {
+	gob.Register(&fileBuffer{})
+}
+
+func (buf *fileBuffer) MarshalBinary() ([]byte, error) {
+	fullpath, err := filepath.Abs(filepath.Dir(buf.file.Name()))
+	if err != nil {
+		return nil, err
+	}
+	base := filepath.Base(buf.file.Name())
+	buf.file.Close()
+
+	buffer := bytes.NewBuffer(nil)
+	fmt.Fprintln(buffer, filepath.Join(fullpath, base))
+	fmt.Fprintln(buffer, buf.Wrapper.N, buf.Wrapper.L, buf.Wrapper.O)
+	return buffer.Bytes(), nil
+}
+
+func (buf *fileBuffer) UnmarshalBinary(data []byte) error {
+	buffer := bytes.NewBuffer(data)
+	var filename string
+	var N, L, O int64
+	_, err := fmt.Fscanln(buffer, &filename)
+	if err != nil {
+		return err
+	}
+
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	buf.file = file
+
+	_, err = fmt.Fscanln(buffer, &N, &L, &O)
+	buf.Wrapper = wrapio.NewWrapper(file, L, O, N)
+	return err
+}