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/discard.go

@@ -0,0 +1,36 @@
+package buffer
+
+import (
+	"encoding/gob"
+	"io"
+	"io/ioutil"
+	"math"
+)
+
+type discard struct{}
+
+// Discard is a Buffer which writes to ioutil.Discard and read's return 0, io.EOF.
+// All of its methods are concurrent safe.
+var Discard Buffer = discard{}
+
+func (buf discard) Len() int64 {
+	return 0
+}
+
+func (buf discard) Cap() int64 {
+	return math.MaxInt64
+}
+
+func (buf discard) Reset() {}
+
+func (buf discard) Read(p []byte) (n int, err error) {
+	return 0, io.EOF
+}
+
+func (buf discard) Write(p []byte) (int, error) {
+	return ioutil.Discard.Write(p)
+}
+
+func init() {
+	gob.Register(&discard{})
+}