protobuf{2,3}-cpp: add notes

Author: suhailskhan

devel/protobuf2-cpp/Portfile

@@ -32,6 +32,22 @@ long_description \
                 name-value pairs.
 homepage        https://github.com/google/protobuf
 
+notes-append "
+The '${name}' port contains the legacy Protocol Buffers v2 C++
+implementation.
+
+To avoid file clashes with the modern 'protobuf' port, all headers, libraries,
+and the 'protoc' compiler are now installed under ${prefix}/libexec/${name}.
+
+This port may potentially be removed in the near future.
+Wherever possible, please migrate builds and scripts to depend on the
+'protobuf' port instead.
+
+If you would like to continue using this port's 'protoc' compiler in the
+interim, add it to your PATH, e.g.:
+   export PATH=${prefix}/libexec/${name}/bin:\$PATH
+"
+
 distname        protobuf-${version}
 dist_subdir     protobuf-cpp
 worksrcdir      protobuf-${version}

devel/protobuf3-cpp/Portfile

@@ -40,6 +40,22 @@ long_description \
                 name-value pairs.
 homepage        https://protobuf.dev
 
+notes-append "
+The '${name}' port contains the legacy Protocol Buffers v3 C++
+implementation.
+
+To avoid file clashes with the modern 'protobuf' port, all headers, libraries,
+and the 'protoc' compiler are now installed under ${prefix}/libexec/${name}.
+
+This port may potentially be removed in the near future.
+Wherever possible, please migrate builds and scripts to depend on the
+'protobuf' port instead.
+
+If you would like to continue using this port's 'protoc' compiler in the
+interim, add it to your PATH, e.g.:
+   export PATH=${prefix}/libexec/${name}/bin:\$PATH
+"
+
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