would-reformat - automatic reformatting for emacs without being annoying

# Motivation

I've never liked it when a text editor formats code for me without my asking.
I don't like it when the editor uses cheap heuristics (indent a new line to
match the previous one?  blah!) and I don't like it when the editor shells out
to one of the new generation of automatic code formatters.

But I don't enjoy formatting code by hand either.  Who does?

This is my solution: some shell scripts and some emacs lisp code.

The shell script `would-reformat.sh` takes a file's full path as
its argument.  It tells you if that file would be reformatted.

The shell script `do-reformat.sh` takes a file's full path as its argument.  It
reformats the file.

Finally, there is some rudimentary machinery to run `would-reformat.sh` when
saving a file and to run `do-reformat.sh` when you hit `<F1>`.

## Supported programming languages and file formats

- python
- go
- javascript
- typescript
- vue
- css
- php
- html
- jsx
- tsx
- css
- cscc
- sh
- dart

Python uses `black`; go uses `gofmt`; dart uses `dart format`.  The rest use
`prettier`.  Adding new programming languages is easy, assuming they have a
formatter with a dry run mode.

# Installation

- Change to the directory where you want to use **would-reformat**:
  `$ cd ~/devel/my-project`
- From that directory, call the script `install.sh` in the directory where
  you have **would-reformat** checked out:
  `you@host:~/devel/my-project $ ~/src/would-reformat/install.sh`

Be sure to run the installation script from the root of your project's
directory, not a subdirectory.

This will do the following:

- create the directory `~/devel/my-project/bin` if it does not exist
- create `~/devel/my-project/bin/_reformat-common.sh`,
  `~/devel/my-project/bin/do-reformat.sh`, and
  `~/devel/my-project/bin/would-reformat.sh` as symlinks to files with
  the same names in `~/src/would-reformat`.
- create `~/devel/my-project/.dir-locals.el` as a symlink to the file
  with the same name in `~/src/would-reformat`.

This should work from a checkout wherever you happen to have it.  It doesn't
need to be in `~/src`.  However, if you remove the checkout, then the symlinks
will break, so don't do that.  If you rename the checkout, the symlinks will break.

The directory `bin` with respect to `my-project` however is hardcoded
(enhancements here are welcome).

The script `install.sh` favors conservatism over cleverness: for example,
if it finds the file `~/devel/my-project/bin/do-reformat.sh` then it
checks whether it is a symlink to `~/src/would-reformat/do-reformat.sh`.
If it is not, then it just prints a warning rather than attempting to correct
the situation.

# Troubleshooting

## nothing works from emacs

Be sure to run the install script from your project's root as determined by
`(projectile-project-root)`.

## problems with nvm, pyenv, goenv, etc

The problem might be that their shims aren't in your `PATH`.  To work around
this sort of problem I run emacs from a wrapper script that ensures the shims
are loaded in my `PATH`.

## Running prettier is slow

The scripts by default call `npx prettier` with some arguments.  If you call
these scripts from a directory where there's a `node_modules/` directory with
prettier and plugins, if necessary, installed, then `npx` should be fast
enough.

The solution, therefore, seems to be to say `yarn add --dev prettier` (or
`npm install --dev prettier`) in the right place.

(This seems to work for me, but it is admittedly still uncomfortably
cargoculty.  There should be a more solid basis for this answer.)

## problems running black

The solution seems to be to run `pip install black pipx` somewhere.

# Development

# Wishlist

- Generalize this beyond emacs
- Add support for more programming languages and file formats
- Clean up shell script code
- Be better at "just working"