Disable the RSS feed in file view for non-branches

Files can have an RSS feed, but those only make sense when taken in the
context of a branch. There is no history to make a feed of on a tag or a
commit: they're static. Forgejo does not provide a feed for them for
this reason.

However, the file view on the web UI was offering a link to these
non-existent feeds. With this patch, it does that no longer, and only
provides a link when viewing the file in the context of a branch.

Fixes #2102.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>

options/locale/locale_en-US.ini

@@ -935,6 +935,8 @@ visibility.private = Private
 visibility.private_tooltip = Visible only to members of organizations you have joined
 
 [repo]
+rss.must_be_on_branch = You must be on a branch to have an RSS feed.
+
 new_repo_helper = A repository contains all project files, including revision history. Already hosting one elsewhere? <a href="%s">Migrate repository.</a>
 owner = Owner
 owner_helper = Some organizations may not show up in the dropdown due to a maximum repository count limit.

templates/repo/view_file.tmpl

@@ -43,9 +43,15 @@
 				<a download href="{{$.RawFileLink}}"><span class="btn-octicon" data-tooltip-content="{{ctx.Locale.Tr "repo.download_file"}}">{{svg "octicon-download"}}</span></a>
 				<a id="copy-content" class="btn-octicon {{if not .CanCopyContent}} disabled{{end}}"{{if or .IsImageFile (and .HasSourceRenderedToggle (not .IsDisplayingSource))}} data-link="{{$.RawFileLink}}"{{end}} data-tooltip-content="{{if .CanCopyContent}}{{ctx.Locale.Tr "copy_content"}}{{else}}{{ctx.Locale.Tr "copy_type_unsupported"}}{{end}}">{{svg "octicon-copy" 14}}</a>
 				{{if .EnableFeed}}
-				<a class="btn-octicon" href="{{$.FeedURL}}/rss/{{$.BranchNameSubURL}}/{{PathEscapeSegments .TreePath}}" data-tooltip-content="{{ctx.Locale.Tr "rss_feed"}}">
+					{{if .IsViewBranch}}
-					{{svg "octicon-rss" 14}}
+						<a class="btn-octicon" href="{{$.FeedURL}}/rss/{{$.BranchNameSubURL}}/{{PathEscapeSegments .TreePath}}" data-tooltip-content="{{ctx.Locale.Tr "rss_feed"}}">
-				</a>
+							{{svg "octicon-rss" 14}}
+						</a>
+					{{else}}
+						<span class="btn-octicon disabled" data-tooltip-content="{{ctx.Locale.Tr "repo.rss.must_be_on_branch"}}">
+							{{svg "octicon-rss" 14}}
+						</span>
+					{{end}}
 				{{end}}
 				{{if .Repository.CanEnableEditor}}
 					{{if .CanEditFile}}

tests/integration/repo_test.go

@@ -406,6 +406,40 @@ func TestViewFileInRepo(t *testing.T) {
 	assert.EqualValues(t, 0, repoSummary.Length())
 }
 
+func TestViewFileInRepoRSSFeed(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	hasFileRSSFeed := func(t *testing.T, ref string) bool {
+		t.Helper()
+
+		req := NewRequestf(t, "GET", "/user2/repo1/src/%s/README.md", ref)
+		resp := MakeRequest(t, req, http.StatusOK)
+
+		htmlDoc := NewHTMLParser(t, resp.Body)
+		fileFeed := htmlDoc.doc.Find(`a[href*="/user2/repo1/rss/"]`)
+
+		return fileFeed.Length() != 0
+	}
+
+	t.Run("branch", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		assert.True(t, hasFileRSSFeed(t, "branch/master"))
+	})
+
+	t.Run("tag", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		assert.False(t, hasFileRSSFeed(t, "tag/v1.1"))
+	})
+
+	t.Run("commit", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		assert.False(t, hasFileRSSFeed(t, "commit/65f1bf27bc3bf70f64657658635e66094edbcb4d"))
+	})
+}
+
 // TestBlameFileInRepo repo description, topics and summary should not be displayed when running blame on a file
 func TestBlameFileInRepo(t *testing.T) {
 	defer tests.PrepareTestEnv(t)()