brew update failure while executing git checkout

Question

After an interrupted brew update because of a network issue, Homebrew appears to be broken:

$ brew update
error: pathspec \'master\' did not match a         


        

Answer 1

I had a similar problem where from /usr/local (== $(brew --prefix)) I tried the answer by @ Julien Carsique but still got the error:

[local]master$ git checkout 3115d85 hdf5.rb
error: pathspec '3115d85' did not match any file(s) known to git.
error: pathspec 'hdf5.rb' did not match any file(s) known to git.

This was because I the hdf5 routine was in /usr/local/Library/tab/homebrew-science which has it's own git repository. To fix this I entered:

[local]master$ cd Library/Taps/homebrew/homebrew-science/
[homebrew-science]master$ git checkout 3115d85 hdf5.rb

Now I can install a previous version of the desired library (e.g. hdf5)

Hope this helps someone!