add test and simplify code

src/matches.rs

@@ -103,12 +103,9 @@ pub(crate) fn rewrite_match(
     let inner_attrs_str = if inner_attrs.is_empty() {
         String::new()
     } else {
-        shape.indent.block_indent(context.config);
-        let result = inner_attrs
-            .rewrite(context, shape)
-            .map(|s| format!("{}{}\n", nested_indent_str, s))?;
-        shape.indent.block_unindent(context.config);
-        result
+        inner_attrs
+            .rewrite(context, shape.block_indent(context.config.tab_spaces()))
+            .map(|s| format!("{}{}\n", nested_indent_str, s))?
     };
 
     let open_brace_pos = if inner_attrs.is_empty() {

tests/source/issue-6147/expect_changed.rs

@@ -0,0 +1,18 @@
+pub fn main() {
+let a = Some(12)
+match a {
+#![attr1]
+#![attr2]
+#![attr3]
+_ => None,
+}
+
+{
+match a {
+#![attr1]
+#![attr2]
+#![attr3]
+_ => None,
+}
+}
+}

tests/target/issue-6147/expect_changed.rs

@@ -0,0 +1,18 @@
+pub fn main() {
+    let a = Some(12)
+    match a {
+        #![attr1]
+        #![attr2]
+        #![attr3]
+            _ => None,
+    }
+
+    {
+        match a {
+            #![attr1]
+            #![attr2]
+            #![attr3]
+                _ => None,
+        }
+    }
+}

tests/target/issue-6147/expect_not_changed.rs

@@ -0,0 +1,18 @@
+pub fn main() {
+    let a = Some(12)
+    match a {
+        #![attr1]
+        #![attr2]
+        #![attr3]
+            _ => None,
+    }
+
+    {
+        match a {
+            #![attr1]
+            #![attr2]
+            #![attr3]
+                _ => None,
+        }
+    }
+}