Add indent_match_arms option (#1404)

Makes it optional whether to indent arms in match expressions. Setting this
to false may be desirable for people wishing to avoid double-indents, in
that if the match arm is a block, the block will cause an extra indentation
level, and if it isn't a block but just a single line, it's still easy to
see the logic at a glance.

This style is preferred in certain other languages with switch statements,
e.g. Linux style C and the most common Java style.

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/source/indent_match_arms.rs b/tests/source/indent_match_arms.rs
new file mode 100644
index 00000000000..ecadbe705ff
--- /dev/null
+++ b/tests/source/indent_match_arms.rs
@@ -0,0 +1,27 @@
+// rustfmt-indent_match_arms: false
+
+fn main() {
+    match x {
+        1 => "one",
+        2 => "two",
+        3 => "three",
+        4 => "four",
+        5 => "five",
+        _ => "something else",
+    }
+
+    match x {
+        1 => "one",
+        2 => "two",
+        3 => "three",
+        4 => "four",
+        5 => match y {
+            'a' => 'A',
+            'b' => 'B',
+            'c' => 'C',
+            _ => "Nope",
+        },
+        _ => "something else",
+    }
+
+}