Imagine if you could use pacman to install binary packages as well as build those same packages from source (with your own optimizations). Not only that, but upgrades remembered which packages were precompiled and which were compiled on the spot.
Now, imagine that pacman didn't actually handle it, because the hard-core KISS people would complain too much and you wouldn't be able to think while you watch gcc output fly by. Imagine instead a wrapper around pacman that handled it for you.
Enter srcpac. Lights brighten, music comes to a peak, close up!
srcpac acts exactly the same as pacman (well, it should anyway), except you get this little extra flag -b (or --build) tacked on to -S (--sync) to build from source instead of install from a binary package.
Let's see an example:
srcpac -Sb w3m
will compile w3m, install it, and remember that it was compiled
srcpac -Sybu
will upgrade all the packages that need upgrading by building them and remember that they were compiled (be careful with this one, it will include packages that weren't previously compiled).
srcpac -Syu
will upgrade all binary packages by installing binaries and upgrade all source packages by compiling from source.
srcpac -Qi w3m adds an extra line too, "Source", with a simple yes or no.
You can install srcpac with pacman -S srcpac. From then on you want to use srcpac instead of pacman.
I've also added the support for package configs. Have a look at the example /etc/srcpac.conf entry.
The released version also adds the -o option to -S. This will apply config changes and less the PKGBUILDs without doing any building.
BEWARE: the -r option isn't fully implemented and may install to / in some cases, I'm pretty sure I don't ever write to / when -r is specified, but I can't be sure.