prezto/plugins/git/functions/git-hub

# Open the GitHub repository in the browser.
local remote branches branch current_branch url

remote="${1:-origin}"
url=$(
  git config -l \
    | grep "remote.${remote}.url" \
    | sed -En "s/remote.${remote}.url=(git|https?)(@|:\/\/)github.com(:|\/)(.+)\/(.+).git/https:\/\/github.com\/\4\/\5/p"
)
branches=($(
  git branch -a \
    | grep "remotes/${remote}" \
    | sed -e 's/[ \*]*//g' -e "s:remotes/${remote}/::g"
))
current_branch="$(git-branch)"
branch="${2:-master}"

if [[ -z "$2" ]]; then
  if (( $branches[(I)$current_branch] != 0 )); then
    branch="$current_branch"
  else
    branch='master'
  fi
fi

if [[ -n "$url" ]]; then
  url="${url}/tree/${branch}"

  if (( $+commands[$BROWSER] )); then
    "$BROWSER" "$url"
    return 0
  else
    print "fatal: Browser not set or set to a non-existent browser." >&2
    return 1
  fi
else
  print "fatal: Not a Git repository or origin remote not set." >&2
  return 1
fi