Using ~/.emacs.d this way came about well before git was invented. :)

sigjuice · on July 29, 2017

Really? C-h v user-emacs-directory RET says programs in Emacs store information in this directory. To me, this says ~/.emacs.d/ is not intended for humans.

  user-emacs-directory is a variable defined in ‘subr.el’.
  Its value is "~/.emacs.d/"

    This variable may be risky if used as a file-local variable.

  Documentation:
  Directory beneath which additional per-user Emacs-specific files are placed.
  Various programs in Emacs store information in this directory.
  Note that this should end with a directory separator.
  See also ‘locate-user-emacs-file’.

db48x · on July 29, 2017

It happened in 2002, and git was started in 2005. See commit a04d5983:

    commit a04d59830e46664faa4d534366a6b07e3b7c12f2
    Author: Richard M. Stallman <[email protected]>
    Date:   Sat Oct 26 22:41:33 2002 +0000
        (command-line): Look for .emacs under ~/.emacs.d after looking in ~.

Interestingly it was changed to look for ~/.emacs.d/init.el in 2005, six months after git got started.

See also chapter 51.4 of the Emacs manual (which is often preferred over the documentation of variables simply because it can be more explanatory):

    51.4 The Emacs Initialization File
    ==================================
    
    When Emacs is started, it normally tries to load a Lisp program from an
    “initialization file”, or “init file” for short.  This file, if it
    exists, specifies how to initialize Emacs for you.  Emacs looks for your
    init file using the filenames ‘~/.emacs’, ‘~/.emacs.el’, or
    ‘~/.emacs.d/init.el’; you can choose to use any one of these three names
    (*note Find Init::).  Here, ‘~/’ stands for your home directory.

So yes, it's long been used for things like the list of recently opened files, and configuration changes you made with Custom, and the UIDVALIDITY of your IMAP folders and so on, but it's also been a place to put your init file for quite a long time as well. Once you get a longish init.el file, it's a pretty short step to making several .el files that you load from init.el, and from there you can get as fancy as you like.

omaranto · on July 29, 2017

Programs and humans can peacefully coexist. Emacs looks for your init.el in that directory so it is most definitely also meant for people to use. I put my own libraries in ~/.emacs.d/my-lisp (and I put this directory on the load path). I've had zero trouble with this setup.