How to run pdfcrop when using \includegraphics with a PDF?

When the shell escape feature (--shell-escape or --enable-write18 (MiKTeX)) is enabled, the conversion can be called via \immediate\write18{...}:

\immediate\write18{pdfcrop image.pdf}%
\includegraphics{image-crop}

The conversion can be limited to the cases, where the cropped image file not yet exists:

\IfFileExists{image-crop.pdf}{}{\immediate\write18{pdfcrop image.pdf}}%
\includegraphics{image-crop}