Add API to serve blob or LFS file content (#19689)

* Add LFS API

* Update routers/api/v1/repo/file.go

Co-authored-by: Gusted <williamzijl7@hotmail.com>

* Apply suggestions

* Apply suggestions

* Update routers/api/v1/repo/file.go

Co-authored-by: Gusted <williamzijl7@hotmail.com>

* Report errors

* ADd test

* Use own repo for test

* Use different repo name

* Improve handling

* Slight restructures

1. Avoid reading the blob data multiple times
2. Ensure that caching is only checked when about to serve the blob/lfs
3. Avoid nesting by returning early
4. Make log message a bit more clear
5. Ensure that the dataRc is closed by defer when passed to ServeData

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Gusted <williamzijl7@hotmail.com>
Co-authored-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

integrations/api_repo_file_get_test.go

@@ -0,0 +1,56 @@
+// Copyright 2022 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"
+	"net/url"
+	"os"
+	"testing"
+
+	api "code.gitea.io/gitea/modules/structs"
+	"code.gitea.io/gitea/modules/util"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAPIGetRawFileOrLFS(t *testing.T) {
+	defer prepareTestEnv(t)()
+
+	// Test with raw file
+	req := NewRequest(t, "GET", "/api/v1/repos/user2/repo1/media/README.md")
+	resp := MakeRequest(t, req, http.StatusOK)
+	assert.Equal(t, "# repo1\n\nDescription for repo1", resp.Body.String())
+
+	// Test with LFS
+	onGiteaRun(t, func(t *testing.T, u *url.URL) {
+		httpContext := NewAPITestContext(t, "user2", "repo-lfs-test")
+		doAPICreateRepository(httpContext, false, func(t *testing.T, repository api.Repository) {
+			u.Path = httpContext.GitPath()
+			dstPath, err := os.MkdirTemp("", httpContext.Reponame)
+			assert.NoError(t, err)
+			defer util.RemoveAll(dstPath)
+
+			u.Path = httpContext.GitPath()
+			u.User = url.UserPassword("user2", userPassword)
+
+			t.Run("Clone", doGitClone(dstPath, u))
+
+			dstPath2, err := os.MkdirTemp("", httpContext.Reponame)
+			assert.NoError(t, err)
+			defer util.RemoveAll(dstPath2)
+
+			t.Run("Partial Clone", doPartialGitClone(dstPath2, u))
+
+			lfs, _ := lfsCommitAndPushTest(t, dstPath)
+
+			reqLFS := NewRequest(t, "GET", "/api/v1/repos/user2/repo1/media/"+lfs)
+			respLFS := MakeRequestNilResponseRecorder(t, reqLFS, http.StatusOK)
+			assert.Equal(t, littleSize, respLFS.Length)
+
+			doAPIDeleteRepository(httpContext)
+		})
+	})
+}