If I do a recursive "Find in Files" and specify the extra option --include "*.[ch]" the search always comes up empty. If I leave out the option the search finds the documents containing my search term.
If I repeat the search on the command line using grep and the options that geany shows me, then grep does find the files I want (C and H-files):
$ grep -nHlifr --include "*.[ch]" -- abcd *
I tried different formats for --include: "*.[ch]", '*.[ch]' and \*.\[ch\]
They all don't work with geany but they do work on the commandline.
I'm using geany 0.19.1 "Vellam" and GNU grep 2.6.3 on Debian Squeeze 2.6.32-5-amd64.