Bug#379007: update-grub updates default index incorrectly when one kernel version is a prefix of another

[Max Bowsher]

Package: grub
Version: 0.97-12
Severity: normal

Suppose you have kernel 2.6.15-1-somearch installed, and also have
2.6.15-1-somearch-somesuffix.

If you set the default kernel to 2.6.15-1-somearch, and run update-grub
with grub's 'update the default setting to continue pointing to the same
kernel' setting switched on, it resets the default to point at
2.6.15-1-somearch-somesuffix!

This is because in the grep used to find the proper line, there is no
end anchor, so 2.6.15-1-somearch-somesuffix matches when grub is looking
for 2.6.15-1-somearch.

(Also, the grep didn't seem to be making any attempt to escape regexp
metacharacters - since kernel versions always contain '.', this could be
potentially hazardous too.)