Add single commit API support (#5843)

* add single commit API support

integrations/api_repo_git_commits_test.go

@@ -0,0 +1,32 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package integrations
+
+import (
+	"net/http"
+	"testing"
+
+	"code.gitea.io/gitea/models"
+)
+
+func TestAPIReposGitCommits(t *testing.T) {
+	prepareTestEnv(t)
+	user := models.AssertExistsAndLoadBean(t, &models.User{ID: 2}).(*models.User)
+	// Login as User2.
+	session := loginUser(t, user.Name)
+	token := getTokenForLoggedInUser(t, session)
+
+	for _, ref := range [...]string{
+		"commits/master", // Branch
+		"commits/v1.1",   // Tag
+	} {
+		req := NewRequestf(t, "GET", "/api/v1/repos/%s/repo1/git/%s?token="+token, user.Name, ref)
+		session.MakeRequest(t, req, http.StatusOK)
+	}
+
+	// Test getting non-existent refs
+	req := NewRequestf(t, "GET", "/api/v1/repos/%s/repo1/git/commits/unknown?token="+token, user.Name)
+	session.MakeRequest(t, req, http.StatusNotFound)
+}