Add googletest to write unit tests for pi.proto

Added it as a submodule rather than copying whole code, but using my own
makefile. Only compiled when running 'make check' and if configure was
run with '--with-proto' (since we are only going to write unit tests for
pi.proto and proto frontend at first).

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "proto/googleapis"]
 	path = proto/googleapis
 	url = https://github.com/googleapis/googleapis.git
+[submodule "third_party/googletest"]
+	path = third_party/googletest
+	url = https://github.com/google/googletest

configure.ac

@@ -43,6 +43,9 @@ AS_IF([test "$with_proto" = yes && test "$want_fe_cpp" = no], [
 AM_CONDITIONAL([WITH_FE_CPP], [test "$want_fe_cpp" = yes])
 
 AM_CONDITIONAL([WITH_PROTO], [test "$with_proto" = yes])
+# may add other conditions later for GTEST to be compiled if we use GTEST
+# somewhere else
+AM_CONDITIONAL([WITH_GTEST], [test "$with_proto" = yes])
 
 AC_ARG_WITH([internal-rpc],
     AS_HELP_STRING([--with-internal-rpc],

proto/Makefile.am

@@ -14,7 +14,7 @@ $(srcdir)/google/rpc/code.proto \
 $(srcdir)/device.proto \
 $(srcdir)/resource.proto
 
-EXTRA_DIST = $(protos) google
+EXTRA_DIST = $(protos)
 
 proto_cpp_files = \
 cpp_out/pi.pb.cc \

third_party/Makefile.am

@@ -1,3 +1,7 @@
 ACLOCAL_AMFLAGS = ${ACLOCAL_FLAGS} -I m4
 
+if WITH_GTEST
+include gtest.am
+endif
+
 SUBDIRS = cJSON unity

third_party/gtest.am

@@ -0,0 +1,45 @@
+check_LTLIBRARIES = libgtest.la
+
+libgtest_la_CPPFLAGS = \
+-I$(srcdir)/googletest/googletest/include \
+-I$(srcdir)/googletest/googletest
+
+EXTRA_DIST = \
+googletest/googletest/include/gtest/gtest-printers.h \
+googletest/googletest/include/gtest/gtest-test-part.h \
+googletest/googletest/include/gtest/internal/custom/gtest-printers.h \
+googletest/googletest/include/gtest/internal/custom/gtest.h \
+googletest/googletest/include/gtest/internal/custom/gtest-port.h \
+googletest/googletest/include/gtest/internal/gtest-internal.h \
+googletest/googletest/include/gtest/internal/gtest-port-arch.h \
+googletest/googletest/include/gtest/internal/gtest-port.h \
+googletest/googletest/include/gtest/internal/gtest-type-util.h \
+googletest/googletest/include/gtest/internal/gtest-tuple.h \
+googletest/googletest/include/gtest/internal/gtest-linked_ptr.h \
+googletest/googletest/include/gtest/internal/gtest-string.h \
+googletest/googletest/include/gtest/internal/gtest-filepath.h \
+googletest/googletest/include/gtest/internal/gtest-param-util.h \
+googletest/googletest/include/gtest/internal/gtest-death-test-internal.h \
+googletest/googletest/include/gtest/internal/gtest-param-util-generated.h \
+googletest/googletest/include/gtest/gtest-param-test.h \
+googletest/googletest/include/gtest/gtest-typed-test.h \
+googletest/googletest/include/gtest/gtest-message.h \
+googletest/googletest/include/gtest/gtest_prod.h \
+googletest/googletest/include/gtest/gtest_pred_impl.h \
+googletest/googletest/include/gtest/gtest-spi.h \
+googletest/googletest/include/gtest/gtest-death-test.h
+
+EXTRA_DIST += \
+googletest/googletest/src/gtest-test-part.cc \
+googletest/googletest/src/gtest-filepath.cc \
+googletest/googletest/src/gtest-typed-test.cc \
+googletest/googletest/src/gtest-port.cc \
+googletest/googletest/src/gtest_main.cc \
+googletest/googletest/src/gtest-death-test.cc \
+googletest/googletest/src/gtest.cc \
+googletest/googletest/src/gtest-printers.cc \
+googletest/googletest/src/gtest-internal-inl.h
+
+libgtest_la_SOURCES = \
+googletest/googletest/src/gtest-all.cc \
+googletest/googletest/include/gtest/gtest.h