#+title: Help keeping ~/.config/emacs clean

The default paths used to store configuration files and persistent
data are not consistent across Emacs packages.  This isn't just a
problem with third-party packages but even with built-in packages.

Some packages put these files directly in ~user-emacs-directory~
or ~$HOME~ or in a subdirectory of either of the two or elsewhere.
Furthermore sometimes file names are used that don't provide any
insight into what package might have created them.

This package sets out to fix this by changing the values of path
variables to put configuration files in ~no-littering-etc-directory~
(defaulting to "etc/" under ~user-emacs-directory~, thus usually
"$HOME/.config/emacs/etc/") and persistent data files in
~no-littering-var-directory~ (defaulting to "var/" under
~user-emacs-directory~, thus usually "$HOME/.config/emacs/var/"), and
by using descriptive file names and subdirectories when appropriate.
This is similar to a color-theme; a "path-theme" if you will.

We still have a long way to go until most built-in and many
third-party path variables are properly "themed".  Like a color-theme,
this package depends on user contributions to accomplish decent
coverage.  Pull requests are highly welcome (but please follow the
conventions described below and in the pull request template).

This package does not automatically migrate existing files to their
new locations, but unless you want to, you also do not have to do
it completely by hand.  The contributed [[./migrate.org][migrate.org]] provides some
guidance and tools to help with the migration.

** Usage

Load the feature ~no-littering~ as early as possible in your init
file.  Make sure you load it at least before you change any path
variables using some other method.

#+begin_src emacs-lisp
  (require 'no-littering)
#+end_src

If you would like to use base directories different from what
~no-littering~ uses by default, then you have to set the respective
variables before loading the feature.

#+begin_src emacs-lisp
  (eval-and-compile ; Ensure values don't differ at compile time.
    (setq no-littering-etc-directory
          (expand-file-name "config/" user-emacs-directory))
    (setq no-littering-var-directory
          (expand-file-name "data/" user-emacs-directory))
    (require 'no-littering))
#+end_src

*** Suggested Settings
**** Auto-save, backup and undo-tree files

Creating backups increases the odds that secret information, which
would otherwise never be stored in clear text, is written to disk.
Likewise backups increase the odds that leaked secrets persist longer.

This topic is beyond the scope of this documentation, but as the
author of this package, I want to at least ensure that its use does
not make matters worse.

For that reason, simply loading ~no-littering~, does not theme the
built-in backup and auto-save functionality, and the third-party
~undo-tree~ package.

A function ~no-littering-theme-backups~ is provided, which does theme
these features.  Before calling that function from your init files,
you should read its docstring and implementation.

**** Lock files

To put lock files into a single repository, you could use something
like the following.  See the docstring to learn about reasons why you
might want to refrain from doing that.

#+begin_src emacs-lisp
  (let ((dir (no-littering-expand-var-file-name "lock-files/")))
    (make-directory dir t)
    (setq lock-file-name-transforms `((".*" ,dir t))))
#+end_src

**** Recent files

If you use ~recentf~ then you might find it convenient to exclude all
of the files in the ~no-littering~ directories using something like
the following.

#+begin_src emacs-lisp
  (require 'recentf)
  (add-to-list 'recentf-exclude
               (recentf-expand-file-name no-littering-var-directory))
  (add-to-list 'recentf-exclude
               (recentf-expand-file-name no-littering-etc-directory))
#+end_src

**** Saved customizations

Emacs will save [[https://www.gnu.org/software/emacs/manual/html_node/emacs/Saving-Customizations.html][customizations]] into your ~init.el~ file by default.
If you don't want that, you might want to store them in a sibling file
or even in the ~etc/~ directory:

#+begin_src emacs-lisp
  (setq custom-file (expand-file-name "custom.el" user-emacs-directory))
  ;; or
  (setq custom-file (no-littering-expand-etc-file-name "custom.el"))
#+end_src

**** Native compilation cache

When using Emacs 29, the location of the native compilation cache can
be changed using a function, preferably in ~early-init.el~:

#+begin_src emacs-lisp
  (when (and (fboundp 'startup-redirect-eln-cache)
             (fboundp 'native-comp-available-p)
             (native-comp-available-p))
    (startup-redirect-eln-cache
     (convert-standard-filename
      (expand-file-name  "var/eln-cache/" user-emacs-directory))))
#+end_src

** Conventions

The conventions do not cover every edge-case and are not set in stone.
If you feel it is appropriate to diverge from what is outlined below,
then do so, *but provide justification* in the /commit message/.

Likewise if you are unsure if you interpreted a convention correctly,
just make a best effort, *but mention it* in the /pull-request message/,
so we can improve the wording if necessary.

Generally there is no need to open an issue first; the maintainers can
amend to your commit if necessary, or ask you to do so.

*** Using the checklist

Each item below is prefixed with a checkbox to make it easier to not
forget about some of them.  Unfortunately these checkboxes cannot
actually be checked on Github.  Instead you have to either open the
~README.org~ file in Emacs and then use ~C-c C-c~ to check a box, or use
the [[https://docs.emacsmirror.org/no-littering][interactive checklist]] in a browser.

*** (A) File names

1. [ ] *File names are based on the name of the respective Emacs lisp*
   *variables and the name of the respective Emacs package.*

2. [ ] The name of the respective Emacs package should serve as the
   prefix of the file name, unless the file is in a subdirectory in
   which case the name of the subdirectory serves as the prefix.

3. [ ] If the name of the package and the prefix of the variable do
   not match, then we prefer the name of the package.

4. [ ] If the name of a path variable ends with ~-file~, ~-default-file~,
   ~-directory~, ~-default-directory~, or something similar, then that
   suffix is usually dropped from the file name.

5. [ ] If applicable, the appropriate extension is added to the file
   name so that files are visited using the appropriate major-modes
   and also to provide a hint about the kind of data stored in the
   file.  E.g., if a file contains an S-expression, then the suffix
   should be ~.eld~.

   (In the past we used ~.el~ instead, because ~.eld~ did not exist yet.
   Many themed files still use the ~.el~ suffix, and I do not plan to
   update them to the preferred ~.eld~ suffix any time soon.  But for
   newly themed files ~.eld~ should be preferred in most cases.)

*** (B) File location and subdirectories

1. [ ] If a package has only one data file, then that is usually
   placed in ~no-littering-var-directory~ itself.  Likewise if a package
   has only one config file, then that is placed in
   ~no-littering-etc-directory~ itself.

2. [ ] If a package has multiple data (or config files), then those
   files are placed in a subdirectory of ~no-littering-var-directory~
   (or ~no-littering-etc-directory~).

3. [ ] If a subdirectory is used for a package's data (or config) file
   variables, then the name of the directory should match the name of
   the package in most cases. The subdirectory name may serve as the
   package prefix of the file name.

4. [ ] If a package provides a "framework" for other packages to use,
   then we may reuse its directories for other packages that make use
   of that framework or otherwise "extend" the "main package".  E.g.,
   we place all ~helm~ related files in ~helm/~.

5. [ ] If a package only defines a single variable that specifies a
   data (or config) directory, then the directory name should
   nevertheless be just the package name.  E.g., the path used for
   ~sx-cache-directory~ from the ~sx~ package is ~sx/cache/~, not ~sx-cache/~.

6. [ ] However if the name of the directory variable implies that the
   package won't ever define any data (or config) files that won't be
   placed in that directory, then we use a top-level directory.  E.g.,
   when the name of the variable is ~<package>-directory~, in which case
   we would use just ~<package>/~ as the path.

*** (C) Ordering and alignment

1. [ ] The code that sets the values of themed variables is split into
   two groups.  The first group sets the value of variables that
   belong to packages that are part of Emacs, and the second group is
   used for variables that are defined by packages that are not part
   of Emacs.

2. [ ] *Each of these lists is sorted alphabetically* (usually by
   variable name).  Please keep it that way.

3. [ ] We attempt to align the value forms inside different ~setq~
   forms.  If the symbol part for a particular variable is too long to
   allow doing so, then don't worry about it and just break the
   alignment.  If it turns out that this happens very often, then we
   will adjust the alignment eventually.

*** (D) Commit messages

1. [ ] Please theme each package using a separate commit and use
   commit messages of the form

   #+begin_src text
     foo: Theme foo-config-file
   #+end_src

   In the commit message /summary line/, we do /not/ quote variable names.

2. [ ] If a package has several path variables, then you should theme
   them all in one commit.

3. [ ] If the variable names do not fit nicely on the summary line,
   then use a message such as:

   #+begin_src text
     foo: Theme variables

     Theme `foo-config-file', `foo-cache-directory',
     and `foo-persistent-file'.
   #+end_src

   In the commit message /body/, we do quote variable names (using Emacs
   lisp docstring quoting, as shown above).

4. [ ] When appropriate add statements like the following to the
   commit message:

   - This file is used to store an s-expression.
   - This file is used to store raw text.
   - This is the only configuration/data file of the package.
   - This package does/doesn't take care of creating the containing
     directory if necessary.  (If the package does not do it, then you
     should also fix that and submit an pull-request in the package's
     repository.)

5. [ ] If you are uncertain, then be explicit about it by adding a
   comment to the pull-request.

*** (E) Pull-request

1. [ ] Please use a dedicated feature branch.  See [[https://github.com/magit/magit/wiki/Dedicated-pull-request-branches][this explanation]] to
   learn why we ask for that.

2. [ ] Please include a link to the package repository in the
   description of the pull-request.

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