[pacman-dev] Warn about using -Sy

[Evangelos Foutras]

Oftentimes, I come across people using `pacman -Sy <name>' to install
new packages. This installs the latest version of a package, while
leaving any required libraries at their old version. The introduction
of an incompatibility between a package and its dependencies is highly
possible.

A recent example of this issue is [1].

Could you please review the attached tiny patch for code structure,
language used, and overall approach?

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[1] http://mailman.archlinux.org/pipermail/arch-general/2010-November/017198.html