Gitignore - Exclude all except specific subdirectory

.gitignore

#
# If all files excluded and you will include only specific sub-directories
# the parent path must matched before.
#

/**
!/.gitignore

###############################
# Un-ignore the affected subdirectory
!/libraries/
# Ignore subdirectory and all including directories and files to match pattern as valid for the next pattern
/libraries/**
# This pattern only works with the two previous patterns
# (i remember it was working alone on older git versions)
!/libraries/myLibrary/
###############################

# Another example
!/templates/
/templates/**
!/templates/myTemplate/