perf_runner seems to leave local tree in an odd state

[thomasvl]

Synced to d3b0879, Performance/perf_runner.sh -c 7b786f134df64c46baa9c7f63daced6af6211c01 finished with files in a locally modified state.

$ git status
On branch master
Your branch is up-to-date with 'origin/master'.

Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

	modified:   Protos/generated_swift_names_enum_cases.proto
	modified:   Protos/generated_swift_names_enums.proto
	modified:   Protos/generated_swift_names_fields.proto
	modified:   Protos/generated_swift_names_messages.proto
	modified:   Reference/generated_swift_names_enum_cases.pb.swift
	modified:   Reference/generated_swift_names_enums.pb.swift
	modified:   Reference/generated_swift_names_fields.pb.swift
	modified:   Reference/generated_swift_names_messages.pb.swift
	modified:   Sources/SwiftProtobuf/BinaryEncoder.swift
	modified:   Sources/SwiftProtobuf/BinaryEncodingVisitor.swift
	modified:   Sources/SwiftProtobuf/Message+BinaryAdditions.swift
	modified:   Tests/SwiftProtobufTests/generated_swift_names_enum_cases.pb.swift
	modified:   Tests/SwiftProtobufTests/generated_swift_names_enums.pb.swift
	modified:   Tests/SwiftProtobufTests/generated_swift_names_fields.pb.swift
	modified:   Tests/SwiftProtobufTests/generated_swift_names_messages.pb.swift

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   Protos/generated_swift_names_enum_cases.proto
	modified:   Protos/generated_swift_names_enums.proto
	modified:   Protos/generated_swift_names_fields.proto
	modified:   Protos/generated_swift_names_messages.proto
	modified:   Reference/generated_swift_names_enum_cases.pb.swift
	modified:   Reference/generated_swift_names_enums.pb.swift
	modified:   Reference/generated_swift_names_fields.pb.swift
	modified:   Reference/generated_swift_names_messages.pb.swift
	modified:   Sources/SwiftProtobuf/BinaryEncoder.swift
	modified:   Sources/SwiftProtobuf/BinaryEncodingVisitor.swift
	modified:   Sources/SwiftProtobuf/Message+BinaryAdditions.swift
	modified:   Tests/SwiftProtobufTests/generated_swift_names_enum_cases.pb.swift
	modified:   Tests/SwiftProtobufTests/generated_swift_names_enums.pb.swift
	modified:   Tests/SwiftProtobufTests/generated_swift_names_fields.pb.swift
	modified:   Tests/SwiftProtobufTests/generated_swift_names_messages.pb.swift

It seems like everything gets backed out locally and the added and then reverted locally. So a git reset HEAD . makes it all go away, but it makes me wonder if the tests are actually testing what is intended.