convenience bash function to git checkout whatever branch matches the passed-in substring

git-co-function.sh

# git-co
# git checkout whatever branch matches the passed-in substring
#
# Argument:
# substring to match
#
# Example:
# git-co sparkles # checks out the branch whose name contains the substring "sparkles"
#
# Will abort with an informative message and no action in various error scenarios.
# If multiple matches are found, they will be listed but not acted on.
#
# alpha software, ymmv, feedback welcome.

git-co () {
  local substring=$1

  # warn if invoked in wrong place
  if [[ ! -d ".git" ]]; then
     echo "not a git directory"
     return
  fi

  # if no arguments, show all the branches we have
  if [[ -z "$substring" ]]; then
     git branch
     return
  fi

  local count=$(git branch | grep "$substring" | wc -l)
  if [[ $count -eq 1 ]]; then
     local branch=$(git branch | grep "$substring" | sed 's/^ \{1,\}//')
     local trimmed=$(echo "$branch" | sed 's/^* //')
     if [[ "$branch" == "$trimmed" ]]; then
        git checkout "$branch"
     else
        echo "already on branch"
        echo "$trimmed"
     fi
  elif [[ $count -eq 0 ]]; then
     echo "no branches found matching $substring"
  else
    echo "mutiple branches found matching $substring:"
    git branch | grep "$substring"
  fi
}