brew updateでエラー

mini:~ admin$ brew update
error: Your local changes to the following files would be overwritten by merge:
	Library/Formula/ffmpeg.rb
Please, commit your changes or stash them before you can merge.
Aborting
Error: Failure while executing: git pull -q origin refs/heads/master:refs/remotes/origin/master

ということでググって先人に助けを乞う。

長いこと更新作業を忘れるとでやすいエラーです.
Homebrewでupdateをしたらエラーが出た - メモ帳

mini:~ admin$ cd `brew --prefix`
mini:/usr/local admin$ git fetch origin
remote: Counting objects: 239, done.
remote: Compressing objects: 100% (99/99), done.
remote: Total 203 (delta 103), reused 180 (delta 81)
Receiving objects: 100% (203/203), 38.27 KiB, done.
Resolving deltas: 100% (103/103), completed with 21 local objects.
From https://github.com/mxcl/homebrew
   8a968e9..d5ecd70  gh-pages   -> origin/gh-pages
 * [new branch]      go         -> origin/go
 * [new branch]      superwip   -> origin/superwip
 * [new branch]      versions   -> origin/versions
hako:/usr/local admin$ git reset --hard origin/master
HEAD is now at b9264bb git: revert to 1.8.2.3
mini:/usr/local admin$ cd
mini:~ admin$ brew update
Already up-to-date.

おけ。

ちなみに

mini:/usr/local admin$ git remote -v
origin	https://github.com/mxcl/homebrew.git (fetch)
origin	https://github.com/mxcl/homebrew.git (push)