[MIT-Scheme-devel] failure updating Git repository

[Taylor R Campbell]

I have never done anything, as far as I know, in this Git repository
beyond various non-destructive commands such as `git log', `git diff',
`git status', &c., and the occasional `git pull' to update it.

% git pull
remote: Counting objects: 325, done.
remote: Compressing objects: 100% (80/80), done.
remote: Total 189 (delta 158), reused 120 (delta 105)
Receiving objects: 100% (189/189), 33.83 KiB, done.
Resolving deltas: 100% (158/158), completed with 121 local objects.
>From git://git.savannah.gnu.org/mit-scheme
 + 645587e...a996c47 HEAD       -> origin/HEAD  (forced update)
error: Ref refs/remotes/origin/master is at 
a996c47f0b70804af9c42cc25b63a14460f56283 but expected 
645587e343ef1f3961fa6f2f0ba08af0bdeddb64
 ! 645587e..d9c4d20  master     -> origin/master  (unable to update local ref)
error: some local refs could not be updated; try running
 'git remote prune origin' to remove any old, conflicting branches

What did I do wrong?  I have no idea what the suggested command `git
remote prune origin' does, but it sounds as though it will
destructively update the remote repository, which is far from what I
want to do.  I hope I didn't screw anything up when I committed a
one-line change to edwin/basic.scm the other week (which I did from a
separate repository, not this clean one which I am trying to update).