egin{figure}[t]
centering
includegraphics[width=0.9columnwidth, clip=true, trim=0 0 0 32]{figures/freq-non-merge.pdf}
includegraphics[width=0.9columnwidth, clip=true, trim=0 0 0 0]{figures/freq-merge.pdf}
caption{Commit frequency before and after the Tvis adoption.}vspace{-0.4cm}
label{fig:freq}
end{figure}
如图：
