The GLSL linker fails if, for example, more than one vertex shader is linked to the same program. This is both valid (per the GLSL spec) and useful. There has been some discussion of this issue on the Xorg mailing list (http://lists.freedesktop.org/archives/xorg/2008-July/037495.html)
This particular problem/case is fixed in git. Full linking still isn't implemented though.
Mass version move, cvs -> git
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