Fix shadowed variable in watchman/PDU.cpp

Summary:
Our upcoming compiler upgrade will require us not to have shadowed variables. Such variables have a _high_ bug rate and reduce readability, so we would like to avoid them even if the compiler was not forcing us to do so.

This codemod attempts to fix an instance of a shadowed variable. Please review with care: if it's failed the result will be a silent bug.

**What's a shadowed variable?**

Shadowed variables are variables in an inner scope with the same name as another variable in an outer scope. Having the same name for both variables might be semantically correct, but it can make the code confusing to read! It can also hide subtle bugs.

This diff fixes such an issue by renaming the variable.

 - If you approve of this diff, please use the "Accept & Ship" button :-)

Reviewed By: palmje

Differential Revision: D64398726

fbshipit-source-id: a9985cd1f1b104cf878dd12b2a3ad51c14b30d26

watchman/PDU.cpp

@@ -581,18 +581,18 @@ ResultErrno<folly::Unit> PduBuffer::jsonEncodeToStream(
 }
 
 ResultErrno<folly::Unit> PduBuffer::pduEncodeToStream(
-    PduFormat format,
+    PduFormat format_2,
     const json_ref& json,
     watchman_stream* stm) {
-  switch (format.type) {
+  switch (format_2.type) {
     case is_json_compact:
       return jsonEncodeToStream(json, stm, JSON_COMPACT);
     case is_json_pretty:
       return jsonEncodeToStream(json, stm, JSON_INDENT(4));
     case is_bser:
-      return bserEncodeToStream(1, format.capabilities, json, stm);
+      return bserEncodeToStream(1, format_2.capabilities, json, stm);
     case is_bser_v2:
-      return bserEncodeToStream(2, format.capabilities, json, stm);
+      return bserEncodeToStream(2, format_2.capabilities, json, stm);
     case need_data:
     default:
       return EINVAL;