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/spill.go

@@ -0,0 +1,41 @@
+package buffer
+
+import (
+	"encoding/gob"
+	"io"
+	"io/ioutil"
+	"math"
+)
+
+type spill struct {
+	Buffer
+	Spiller io.Writer
+}
+
+// NewSpill returns a Buffer which writes data to w when there's an error
+// writing to buf. Such as when buf is full, or the disk is full, etc.
+func NewSpill(buf Buffer, w io.Writer) Buffer {
+	if w == nil {
+		w = ioutil.Discard
+	}
+	return &spill{
+		Buffer:  buf,
+		Spiller: w,
+	}
+}
+
+func (buf *spill) Cap() int64 {
+	return math.MaxInt64
+}
+
+func (buf *spill) Write(p []byte) (n int, err error) {
+	if n, err = buf.Buffer.Write(p); err != nil {
+		m, err := buf.Spiller.Write(p[n:])
+		return m + n, err
+	}
+	return len(p), nil
+}
+
+func init() {
+	gob.Register(&spill{})
+}