how exactly can git config section names contain periods?

  more oddities in my travels, this from Doc.../config.txt:

"The file consists of sections and variables.  A section begins with
the name of the section in square brackets and continues until the
next section begins.  Section names are case-insensitive.  Only
alphanumeric characters, `-` and `.` are allowed in section names.
                                  ^ ?????

  what? how can section names contain periods? reading further,

"Sections can be further divided into subsections. To begin a subsection put its name in double quotes, separated by space from the section name, in the section header, like in the example below:

--------
        [section "subsection"]

  ok, so how on earth would i use "git config" at the command line to
set a config variable with some arbitrary level of subsections? let's
try this:

  $ git config --global a.b.c.d.e rday

huh ... seemed to work fine, and added this to my ~/.gitconfig:

  [a "b.c.d"]
          e = rday

as i see it, the first component is intgerpreted as the section name, the last component is the variable/key(?) name, and everything in between is treated as subsection(s), which is not at all obvious from that Doc file, or from "man git-config".

  and if a section name can contain periods, how would you specify
that at the command line?

rday