Add regression test for current crate intra-doc link

Author: GuillaumeGomez

tests/rustdoc/intra-doc/link-to-current-crate.rs

@@ -0,0 +1,15 @@
+// Test to ensure that we can link to the current crate by using its name.
+
+#![deny(rustdoc::broken_intra_doc_links)]
+#![crate_name = "bar"]
+
+//@ has 'bar/index.html'
+//@ has - '//*[@class="docblock"]//a[@href="index.html"]' 'bar'
+//! [`bar`]
+
+pub mod foo {
+    //@ has 'bar/foo/fn.tadam.html'
+    //@ has - '//*[@class="docblock"]//a[@href="../index.html"]' 'bar'
+    /// [`bar`]
+    pub fn tadam() {}
+}