When submitting multiple commits with one request on ReviewBoard RBTools sets the last commit message as the summary. But, when using the option "--summary” the last commit message is lost and is not written anywhere.
Proposed change stores all commit messages in the description field when both --summary 'text’ and --guess-description options are set.

When a request is send without the "--summary” option the last commit message is written in the summary, as usual.

When a request is send with the "--summary” option the last commit message is written in the description.

When a request is one commit without option "--summary” last commit message is written in the summary, as usual.

When a request comprises one commit then all works as usual.