Can you recommend a way to raise the odds that Quicklisp uses a very good version of SLIME?
how about introducing a branch or a tag for this? either specifically called 'quicklisp' or 'stable', where stable merely means a promise of relative stability compared to the bleeding edge?
i see a problem though: is there a way with git to mark a revision so that the devs can move that mark around unconstrained, while clients can also just git pull without any further action when the mark has been moved (i.e. no need for 'git reset --hard some-old-rev' in case of branches, or 'git tag -d the-moved-tag' or 'git pull -t' in case of tags)?
(the git devs don't want you to move around tags: https://www.kernel.org/pub/software/scm/git/docs/git-tag.html#_on_re_tagging)
if the end solution will specifically be about quicklisp, then this may not be a problem *if* the qicklisp build always clones and never pulls (which i don't know).