I would like for rEFIt to be able to tell GRUB what the chosen OS/Partition is so the user wouldn't need to close the same thing twice, once in rEFIt and later in the GRUB menu.
GRUB should only appear if rEFIt selects the partition containing GRUB unless you installed GRUB to the MBR instead of the Linux partition.
You can edit the GRUB menu file so that the menu does not appear when it boots. Just remove all the other options from the GRUB menu.
rEFIt could tell GRUB what to do only by changing the GRUB menu file and only if it understands the filesystem that menu file is on. The change would last until the menu file is changed again. rEFIt would need to understand the menu file, or it would need to be told exactly what in the menu file to replace (either a line, a string, or the entire file). rEFIt would need to know how to translate a partition in it's menu into a partition number that GRUB understands, or you would need to provide that information in the refit.conf file somehow.
With an EFI-based GRUB, this could theoretically be done by passing options to GRUB or by adjusting settings in NVRAM. I have no idea if the GRUB developers would be amenable to making such changes, though.
IMHO, though, the stated goal ("the user [sh]ouldn't need to [choose] the same thing twice") is better achieved by using rEFInd (my fork of rEFIt, since rEFIt is no longer being maintained), at least if the goal is to boot Linux. rEFInd can launch 3.3.0 and later Linux kernels directly, which cuts GRUB out of the picture entirely. Depending on your needs, using GRUB instead of rEFIt or rEFInd should also work fine, although setting up GRUB as the default boot loader on a Mac is less well-documented as doing the same with rEFIt or rEFInd.
Sign up for the SourceForge newsletter:
You seem to have CSS turned off.
Please don't fill out this field.