/usr/share/doc/ is in protobuf-compiler 2.6.1-1.3.
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..
/usr/share/doc/protobuf-compiler/
/usr/share/doc/protobuf-compiler/README.md.gz
/usr/share/doc/protobuf-compiler/editors/
/usr/share/doc/protobuf-compiler/editors/README.txt
/usr/share/doc/protobuf-compiler/editors/protobuf-mode.el.gz
/usr/share/doc/protobuf-compiler/editors/proto.vim
/usr/share/doc/protobuf-compiler/examples/
/usr/share/doc/protobuf-compiler/examples/addressbook.proto
/usr/share/doc/protobuf-compiler/examples/add_person.cc
/usr/share/doc/protobuf-compiler/examples/README.txt
/usr/share/doc/protobuf-compiler/examples/list_people.py
/usr/share/doc/protobuf-compiler/examples/Makefile
/usr/share/doc/protobuf-compiler/examples/add_person.py
/usr/share/doc/protobuf-compiler/examples/list_people.cc
/usr/share/doc/protobuf-compiler/examples/ListPeople.java
/usr/share/doc/protobuf-compiler/examples/AddPerson.java
/usr/share/doc/protobuf-compiler/CONTRIBUTORS.txt
/usr/share/doc/protobuf-compiler/copyright
/usr/share/doc/protobuf-compiler/changelog.Debian.gz