test(rustfmt): Verify frontmatter is preserved

This is to prove that the frontmatter is preserved.

The choices in tests is intended for showing the different parts of the
proposed Style Guide for frontmatters.

Author: epage

src/tools/rustfmt/tests/source/frontmatter_compact.rs

@@ -0,0 +1,8 @@
+#!/usr/bin/env cargo
+---identifier
+[dependencies]
+regex = "1"
+---
+#![feature(frontmatter)]
+
+fn main() {}

src/tools/rustfmt/tests/source/frontmatter_escaped.rs

@@ -0,0 +1,13 @@
+#!/usr/bin/env cargo
+------------
+package.description = """
+Header
+-----
+
+Body
+"""
+------------
+
+#![feature(frontmatter)]
+
+fn main() {}

src/tools/rustfmt/tests/source/frontmatter_spaced.rs

@@ -0,0 +1,16 @@
+#!/usr/bin/env cargo
+
+
+---   identifier
+[dependencies]
+regex = "1"
+
+---
+
+
+
+
+
+#![feature(frontmatter)]
+
+fn main() {}

src/tools/rustfmt/tests/target/frontmatter_compact.rs

@@ -0,0 +1,8 @@
+#!/usr/bin/env cargo
+---identifier
+[dependencies]
+regex = "1"
+---
+#![feature(frontmatter)]
+
+fn main() {}

src/tools/rustfmt/tests/target/frontmatter_escaped.rs

@@ -0,0 +1,13 @@
+#!/usr/bin/env cargo
+------------
+package.description = """
+Header
+-----
+
+Body
+"""
+------------
+
+#![feature(frontmatter)]
+
+fn main() {}

src/tools/rustfmt/tests/target/frontmatter_spaced.rs

@@ -0,0 +1,16 @@
+#!/usr/bin/env cargo
+
+
+---   identifier
+[dependencies]
+regex = "1"
+
+---
+
+
+
+
+
+#![feature(frontmatter)]
+
+fn main() {}