Refactor git command stdio pipe (#36422)

Most potential deadlock problems should have been fixed, and new code is
unlikely to cause new problems with the new design.

Also raise the minimum Git version required to 2.6.0 (released in 2015)

modules/git/log_name_status.go

@@ -15,25 +15,12 @@ import (
 
 	"code.gitea.io/gitea/modules/container"
 	"code.gitea.io/gitea/modules/git/gitcmd"
-
-	"github.com/djherbis/buffer"
-	"github.com/djherbis/nio/v3"
+	"code.gitea.io/gitea/modules/log"
 )
 
 // LogNameStatusRepo opens git log --raw in the provided repo and returns a stdin pipe, a stdout reader and cancel function
 func LogNameStatusRepo(ctx context.Context, repository, head, treepath string, paths ...string) (*bufio.Reader, func()) {
-	// We often want to feed the commits in order into cat-file --batch, followed by their trees and sub trees as necessary.
-	// so let's create a batch stdin and stdout
-	stdoutReader, stdoutWriter := nio.Pipe(buffer.New(32 * 1024))
-
 	// Lets also create a context so that we can absolutely ensure that the command should die when we're done
-	ctx, ctxCancel := context.WithCancel(ctx)
-
-	cancel := func() {
-		ctxCancel()
-		_ = stdoutReader.Close()
-		_ = stdoutWriter.Close()
-	}
 
 	cmd := gitcmd.NewCommand()
 	cmd.AddArguments("log", "--name-status", "-c", "--format=commit%x00%H %P%x00", "--parents", "--no-renames", "-t", "-z").AddDynamicArguments(head)
@@ -63,16 +50,21 @@ func LogNameStatusRepo(ctx context.Context, repository, head, treepath string, p
 	}
 	cmd.AddDashesAndList(files...)
 
+	stdoutReader, stdoutReaderClose := cmd.MakeStdoutPipe()
+	ctx, ctxCancel := context.WithCancel(ctx)
 	go func() {
-		err := cmd.WithDir(repository).
-			WithStdout(stdoutWriter).
-			RunWithStderr(ctx)
-		_ = stdoutWriter.CloseWithError(err)
+		err := cmd.WithDir(repository).RunWithStderr(ctx)
+		if err != nil && !errors.Is(err, context.Canceled) {
+			log.Error("Unable to run git command %v: %v", cmd.LogString(), err)
+		}
 	}()
 
 	bufReader := bufio.NewReaderSize(stdoutReader, 32*1024)
 
-	return bufReader, cancel
+	return bufReader, func() {
+		ctxCancel()
+		stdoutReaderClose()
+	}
 }
 
 // LogNameStatusRepoParser parses a git log raw output from LogRawRepo