Support relative paths to videos from Wiki pages

This change fixes cases when a Wiki page refers to a video stored
in the Wiki repository using relative path. It follows the similar
case which has been already implemented for images.

Test plan:
- Create repository and Wiki page
- Clone the Wiki repository
- Add video to it, say `video.mp4`
- Modify the markdown file to refer to the video using `<video src="video.mp4">`
- Commit the Wiki page
- Observe that the video is properly displayed

modules/markup/html.go

@@ -407,6 +407,17 @@ func visitNode(ctx *RenderContext, procs []processor, node *html.Node) {
 				attr.Val = camoHandleLink(attr.Val)
 				node.Attr[i] = attr
 			}
+		} else if node.Data == "video" {
+			for i, attr := range node.Attr {
+				if attr.Key != "src" {
+					continue
+				}
+				if len(attr.Val) > 0 && !IsFullURLString(attr.Val) {
+					attr.Val = util.URLJoin(ctx.Links.ResolveMediaLink(ctx.IsWiki), attr.Val)
+				}
+				attr.Val = camoHandleLink(attr.Val)
+				node.Attr[i] = attr
+			}
 		} else if node.Data == "a" {
 			// Restrict text in links to emojis
 			procs = emojiProcessors

modules/markup/html_test.go

@@ -556,6 +556,46 @@ func TestRender_RelativeImages(t *testing.T) {
 		`<img src="`+util.URLJoin(rawwiki, "icon.png")+`"/>`)
 }
 
+func TestRender_RelativeVideos(t *testing.T) {
+	setting.AppURL = markup.TestAppURL
+
+	test := func(input, expected, expectedWiki string) {
+		buffer, err := markdown.RenderString(&markup.RenderContext{
+			Ctx: git.DefaultContext,
+			Links: markup.Links{
+				Base:       markup.TestRepoURL,
+				BranchPath: "master",
+			},
+			Metas: localMetas,
+		}, input)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(string(buffer)))
+		buffer, err = markdown.RenderString(&markup.RenderContext{
+			Ctx: git.DefaultContext,
+			Links: markup.Links{
+				Base: markup.TestRepoURL,
+			},
+			Metas:  localMetas,
+			IsWiki: true,
+		}, input)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.TrimSpace(expectedWiki), strings.TrimSpace(string(buffer)))
+	}
+
+	rawwiki := util.URLJoin(markup.TestRepoURL, "wiki", "raw")
+	mediatree := util.URLJoin(markup.TestRepoURL, "media", "master")
+
+	test(
+		`<video src="Link">`,
+		`<video src="`+util.URLJoin(mediatree, "Link")+`"></video>`,
+		`<video src="`+util.URLJoin(rawwiki, "Link")+`"></video>`)
+
+	test(
+		`<video src="./video.mp4">`,
+		`<video src="`+util.URLJoin(mediatree, "video.mp4")+`"></video>`,
+		`<video src="`+util.URLJoin(rawwiki, "video.mp4")+`"></video>`)
+}
+
 func Test_ParseClusterFuzz(t *testing.T) {
 	setting.AppURL = markup.TestAppURL