protoc: support '=' in --proto_path arguments

src/google/protobuf/compiler/command_line_interface.cc

@@ -1106,8 +1106,13 @@ CommandLineInterface::InterpretArgument(const string& name,
 
       // Make sure disk path exists, warn otherwise.
       if (access(disk_path.c_str(), F_OK) < 0) {
-        std::cerr << disk_path << ": warning: directory does not exist."
-                  << std::endl;
+        // Try the original path; it may have just happed to have a '=' in it.
+        if (access(parts[i].c_str(), F_OK) < 0) {
+          cerr << disk_path << ": warning: directory does not exist." << endl;
+        } else {
+          virtual_path = "";
+          disk_path = parts[i];
+        }
       }
 
       // Don't use make_pair as the old/default standard library on Solaris

src/google/protobuf/compiler/command_line_interface_unittest.cc

@@ -780,6 +780,21 @@ TEST_F(CommandLineInterfaceTest, NonRootMapping) {
   ExpectGenerated("test_generator", "", "bar/foo.proto", "Foo");
 }
 
+TEST_F(CommandLineInterfaceTest, PathWithEqualsSign) {
+  // Test setting up a search path which happens to have '=' in it.
+
+  CreateTempDir("with=sign");
+  CreateTempFile("with=sign/foo.proto",
+    "syntax = \"proto2\";\n"
+    "message Foo {}\n");
+
+  Run("protocol_compiler --test_out=$tmpdir "
+      "--proto_path=$tmpdir/with=sign foo.proto");
+
+  ExpectNoErrors();
+  ExpectGenerated("test_generator", "", "foo.proto", "Foo");
+}
+
 TEST_F(CommandLineInterfaceTest, MultipleGenerators) {
   // Test that we can have multiple generators and use both in one invocation,
   // each with a different output directory.