Use correct README link to render the README (#23152)

`renderReadmeFile` needs `readmeTreelink` as parameter but gets
`treeLink`.
The values of them look like as following:
`treeLink`:  `/{OwnerName}/{RepoName}/src/branch/{BranchName}`
`readmeTreelink`:
`/{OwnerName}/{RepoName}/src/branch/{BranchName}/{ReadmeFileName}`

`path.Dir` in

https://github.com/go-gitea/gitea/blob/8540fc45b11eff9a73753ca139f8ea5c38509bf5/routers/web/repo/view.go#L316
should convert `readmeTreelink` into
`/{OwnerName}/{RepoName}/src/branch/{BranchName}` instead of the current
`/{OwnerName}/{RepoName}/src/branch`.

Fixes #23151

---------

Co-authored-by: Jason Song <i@wolfogre.com>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>

models/fixtures/repository.yml

@@ -25,7 +25,7 @@
   fork_id: 0
   is_template: false
   template_id: 0
-  size: 6708
+  size: 7028
   is_fsck_enabled: true
   close_issues_via_commit_in_any_branch: false
 

routers/web/repo/view.go

@@ -186,7 +186,7 @@ func renderDirectory(ctx *context.Context, treeLink string) {
 		return
 	}
 
-	renderReadmeFile(ctx, readmeFile, treeLink)
+	renderReadmeFile(ctx, readmeFile, fmt.Sprintf("%s/%s", treeLink, readmeFile.name))
 }
 
 // localizedExtensions prepends the provided language code with and without a

tests/gitea-repositories-meta/user2/repo1.git/refs/heads/home-md-img-check

@@ -0,0 +1 @@
+78fb907e3a3309eae4fe8fef030874cebbf1cd5e

tests/integration/repo_test.go

@@ -256,3 +256,23 @@ func TestViewRepoDirectory(t *testing.T) {
 	assert.Zero(t, repoTopics.Length())
 	assert.Zero(t, repoSummary.Length())
 }
+
+func TestMarkDownImage(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	session := loginUser(t, "user2")
+
+	req := NewRequest(t, "GET", "/user2/repo1/src/branch/home-md-img-check")
+	resp := session.MakeRequest(t, req, http.StatusOK)
+
+	htmlDoc := NewHTMLParser(t, resp.Body)
+	_, exists := htmlDoc.doc.Find(`img[src="/user2/repo1/media/branch/home-md-img-check/test-fake-img.jpg"]`).Attr("src")
+	assert.True(t, exists, "Repo home page markdown image link check failed")
+
+	req = NewRequest(t, "GET", "/user2/repo1/src/branch/home-md-img-check/README.md")
+	resp = session.MakeRequest(t, req, http.StatusOK)
+
+	htmlDoc = NewHTMLParser(t, resp.Body)
+	_, exists = htmlDoc.doc.Find(`img[src="/user2/repo1/media/branch/home-md-img-check/test-fake-img.jpg"]`).Attr("src")
+	assert.True(t, exists, "Repo src page markdown image link check failed")
+}