Looking at the documentation for encoding/binary, the only methods for encoding ints
that jump out is PutVarint and PutUvarint. Part of this is because the ByteOrder methods
do not show up in the index (see issue #5860). If you click on these functions in the
index the descriptions read like this:

"PutUvarint encodes a uint64 into buf and returns the number of bytes written. If
the buffer is too small, PutUvarint will panic."

This says nothing about the format. One might assume this uses twos-complement, but this
is not the case. uint(128) would is "8001" (2 bytes) not "80" (1
byte).

There is a paragraph in the Overview (before Index) about it that is easy to skip over:

"Varints are a method of encoding integers using one or more bytes; numbers with
smaller absolute value take a smaller number of bytes. For a specification, see
http://code.google.com/apis/protocolbuffers/docs/encoding.html.";

This information should be in the description of the function.