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/buffer.go

@@ -0,0 +1,48 @@
+// Package buffer implements a series of Buffers which can be composed to implement complicated buffering strategies
+package buffer
+
+import (
+	"io"
+	"os"
+)
+
+// Buffer is used to Write() data which will be Read() later.
+type Buffer interface {
+	Len() int64 // How much data is Buffered in bytes
+	Cap() int64 // How much data can be Buffered at once in bytes.
+	io.Reader   // Read() will read from the top of the buffer [io.EOF if empty]
+	io.Writer   // Write() will write to the end of the buffer [io.ErrShortWrite if not enough space]
+	Reset()     // Truncates the buffer, Len() == 0.
+}
+
+// BufferAt is a buffer which supports io.ReaderAt and io.WriterAt
+type BufferAt interface {
+	Buffer
+	io.ReaderAt
+	io.WriterAt
+}
+
+func len64(p []byte) int64 {
+	return int64(len(p))
+}
+
+// Gap returns buf.Cap() - buf.Len()
+func Gap(buf Buffer) int64 {
+	return buf.Cap() - buf.Len()
+}
+
+// Full returns true iff buf.Len() == buf.Cap()
+func Full(buf Buffer) bool {
+	return buf.Len() == buf.Cap()
+}
+
+// Empty returns false iff buf.Len() == 0
+func Empty(buf Buffer) bool {
+	return buf.Len() == 0
+}
+
+// NewUnboundedBuffer returns a Buffer which buffers "mem" bytes to memory
+// and then creates file's of size "file" to buffer above "mem" bytes.
+func NewUnboundedBuffer(mem, file int64) Buffer {
+	return NewMulti(New(mem), NewPartition(NewFilePool(file, os.TempDir())))
+}