Support abbreviating --release as -r

Of the options people regularly pass to cargo, `--release` seems by far
the most common. Yet even on the command line, we expect people to type
out `--release`.

Add a short version `-r`, and add some tests in the testsuite that
confirm it works.

src/cargo/util/command_prelude.rs

@@ -142,7 +142,7 @@ pub trait AppExt: Sized {
     }
 
     fn arg_release(self, release: &'static str) -> Self {
-        self._arg(opt("release", release))
+        self._arg(opt("release", release).short("r"))
     }
 
     fn arg_profile(self, profile: &'static str) -> Self {

tests/testsuite/build.rs

@@ -1775,6 +1775,25 @@ fn verbose_release_build() {
         .run();
 }
 
+#[cargo_test]
+fn verbose_release_build_short() {
+    let p = project().file("src/lib.rs", "").build();
+    p.cargo("build -v -r")
+        .with_stderr(
+            "\
+[COMPILING] foo v0.0.1 ([CWD])
+[RUNNING] `rustc --crate-name foo src/lib.rs [..]--crate-type lib \
+        --emit=[..]link[..]\
+        -C opt-level=3[..]\
+        -C metadata=[..] \
+        --out-dir [..] \
+        -L dependency=[CWD]/target/release/deps`
+[FINISHED] release [optimized] target(s) in [..]
+",
+        )
+        .run();
+}
+
 #[cargo_test]
 fn verbose_release_build_deps() {
     let p = project()

tests/testsuite/run.rs

@@ -936,6 +936,29 @@ fn release_works() {
     assert!(p.release_bin("foo").is_file());
 }
 
+#[cargo_test]
+fn release_short_works() {
+    let p = project()
+        .file(
+            "src/main.rs",
+            r#"
+                fn main() { if cfg!(debug_assertions) { panic!() } }
+            "#,
+        )
+        .build();
+
+    p.cargo("run -r")
+        .with_stderr(
+            "\
+[COMPILING] foo v0.0.1 ([CWD])
+[FINISHED] release [optimized] target(s) in [..]
+[RUNNING] `target/release/foo[EXE]`
+",
+        )
+        .run();
+    assert!(p.release_bin("foo").is_file());
+}
+
 #[cargo_test]
 fn run_bin_different_name() {
     let p = project()