Commit Tab: show full commit message in a tooltip on mouse over (BB-4107)

When looking at commit messages then sometimes one can only see part of the message, because the column has a fixed size.
It would be nice that as long a commit message is shorter than, say, 1000 chars, that a tooltip pops up which shows the full message.
This way I can stay in the commit view without having to click on the specific message first, in order to be able to read it.

Example:
the full commit message:
{{{
commit: Confirm dialog to add new unknown files is now optional; confirm dialog to delete files is now optional
}}}

But on the commit tab I can only see:
{{{
commit: Confirm dialog to add new unknown files is now optional; confirm dialog to
}}}
and the {{

}} already fades, to indicate that the message continues.