Make sure Objective C Proto compiler doesn't "duplicate" prefixes unnecessarily.
In some cases proto files that want/need to use the objc_class_prefix option have
types that already have the prefix on a subset of their names. In this case we don't
want to duplicate the prefix.
Added tests for this (and prefixes in general).
diff --git a/objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj b/objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj
index eb1e2a8..9f1d825 100644
--- a/objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj
+++ b/objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj
@@ -151,6 +151,7 @@
8B09AAF614B663A7007B4184 /* unittest_objc.proto */ = {isa = PBXFileReference; lastKnownFileType = text; path = unittest_objc.proto; sourceTree = "<group>"; };
8B210CCD159383D60032D72D /* golden_message */ = {isa = PBXFileReference; lastKnownFileType = file; path = golden_message; sourceTree = "<group>"; };
8B210CCF159386920032D72D /* golden_packed_fields_message */ = {isa = PBXFileReference; lastKnownFileType = file; path = golden_packed_fields_message; sourceTree = "<group>"; };
+ 8B35468621A61EB2000BD30D /* unittest_objc_options.proto */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.protobuf; path = unittest_objc_options.proto; sourceTree = "<group>"; };
8B4248B21A8BD96D00BC1EC6 /* UnitTests-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "UnitTests-Bridging-Header.h"; sourceTree = "<group>"; };
8B4248B31A8BD96E00BC1EC6 /* GPBSwiftTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = GPBSwiftTests.swift; sourceTree = "<group>"; };
8B4248DD1A929C7D00BC1EC6 /* Duration.pbobjc.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; name = Duration.pbobjc.h; path = google/protobuf/Duration.pbobjc.h; sourceTree = "<group>"; };
@@ -514,6 +515,7 @@
8BBD9DB016DD1DC8008E1EC1 /* unittest_lite.proto */,
8B7E6A7B14893DBC00F8884A /* unittest_mset.proto */,
8B7E6A7C14893DBC00F8884A /* unittest_no_generic_services.proto */,
+ 8B35468621A61EB2000BD30D /* unittest_objc_options.proto */,
F4CF31711B162EF500BD9B06 /* unittest_objc_startup.proto */,
8B09AAF614B663A7007B4184 /* unittest_objc.proto */,
8B7E6A7D14893DBC00F8884A /* unittest_optimize_for.proto */,
