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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def absolute_git_root_dir(fpath=""):
 """Absolute path to the git root directory containing a given file or directory. """

    if len(fpath) == 0:
        dirname_str = os.getcwd()
    else:
        dirname_str = os.path.dirname(fpath)
    dirname_str = os.path.abspath(dirname_str)
    dirnames = dirname_str.split(os.sep)
    n = len(dirnames)
    for i in xrange(n):
        # is there a .git directory at this level?
        # FIXME hack
        basedir = "/" + os.path.join(*dirnames[0:n - i])
        gitdir = os.path.join(basedir, ".git")
        if os.path.exists(gitdir):
            return basedir