Move git command to git/gitcmd (#35483)

The name cmd is already used in many places and may cause conflicts, so
I chose `gitcmd` instead to minimize potential naming conflicts.

modules/git/gitcmd/command_race_test.go

@@ -0,0 +1,38 @@
+// Copyright 2017 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+//go:build race
+
+package gitcmd
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestRunWithContextNoTimeout(t *testing.T) {
+	maxLoops := 10
+
+	// 'git --version' does not block so it must be finished before the timeout triggered.
+	cmd := NewCommand("--version")
+	for i := 0; i < maxLoops; i++ {
+		if err := cmd.Run(t.Context(), &RunOpts{}); err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+func TestRunWithContextTimeout(t *testing.T) {
+	maxLoops := 10
+
+	// 'git hash-object --stdin' blocks on stdin so we can have the timeout triggered.
+	cmd := NewCommand("hash-object", "--stdin")
+	for i := 0; i < maxLoops; i++ {
+		if err := cmd.Run(t.Context(), &RunOpts{Timeout: 1 * time.Millisecond}); err != nil {
+			if err != context.DeadlineExceeded {
+				t.Fatalf("Testing %d/%d: %v", i, maxLoops, err)
+			}
+		}
+	}
+}