The revision is queried and put into 
config.h by ./configure. As we fix bugs and develop pcb-rnd, we need to 
require to user to rerun ./configure in every few hundred revisions 
normally (see scconfig/Rev.tab). This lets you do very fast, incremental 
builds after svn up, using only make. And you can indeed trust in make, 
and don't have to blindly rerun ./configure and rebuild the whole thing: 
because of Rev.tab the build system tells you when you need to 
reconfigure.
<p>
The price of all these convenience is that the rev number saved in 
config.h will reflect the svn state of the last ./configure, not the last 
compile. So before you install or archive an executable, please do run 
./configure and recompile, even if it isn't required for the build.

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