fix: link refs (#1010)

[![PR App][icn]][demo] | Ref RM-10989
:-------------------:|:----------:

## 🧰 Changes

Globally replaces unnecessary escapes of emphasis characters.

## 🧬 QA & Testing

- [Broken on production][prod].
- [Working in this PR app][demo].


[demo]: https://markdown-pr-PR_NUMBER.herokuapp.com
[prod]: https://SUBDOMAIN.readme.io
[icn]:
https://user-images.githubusercontent.com/886627/160426047-1bee9488-305a-4145-bb2b-09d8b757d38a.svg

__tests__/migration/emphasis.test.ts

@@ -31,4 +31,24 @@ describe('migrating emphasis', () => {
       "
     `);
   });
+
+  it('removes unneccesary escapes from emphasis', () => {
+    const md = `[FOO_BAR] and [FOO__BAR]`;
+    const mdx = migrate(md);
+
+    expect(mdx).toMatchInlineSnapshot(`
+      "[FOO_BAR][FOO_BAR] and [FOO__BAR][FOO__BAR]
+      "
+    `);
+  });
+
+  it('migrates deprecated internal emphasis', () => {
+    const md = `Foo__Bar__Baz`;
+    const mdx = migrate(md);
+
+    expect(mdx).toMatchInlineSnapshot(`
+      "Foo**Bar**Baz
+      "
+    `);
+  });
 });

lib/migrate.ts

@@ -2,7 +2,9 @@ import mdx from './mdx';
 import mdastV6 from './mdastV6';
 
 const migrate = (doc: string): string => {
-  return mdx(mdastV6(doc)).replaceAll(/ /g, ' ');
+  return mdx(mdastV6(doc))
+    .replaceAll(/ /g, ' ')
+    .replaceAll(/(?<!\s)\\_(?!\s)/g, '_');
 };
 
 export default migrate;