git-fmt

(Side note: the formatting component of this project will eventually be split out and named omnifmt.)

git-fmt adds a custom command to Git that automatically formats code by using external pretty-printers. The idea was taken from gofmt, just with a bit of expansion to more languages.

Formatted code is:

• Easier to write: never worry about minor formatting concerns while hacking away.
• Easier to read: when all code looks the same you need not mentally convert others' formatting style into something you can understand.
• Easier to maintain: mechanical changes to the source don't cause unrelated changes to the file's formatting; diffs show only the real changes.
• Uncontroversial: never have a debate about spacing or brace position ever again.

(Bullet points taken from https://blog.golang.org/go-fmt-your-code.)

Installing

Installing git-fmt is easiest done using either stack (recommended) or Cabal. Alternatively you may download a pre-compiled binary of the latest release.

Using stack:

stack install git-fmt
export PATH=$PATH:~/.local/bin

Using Cabal:

cabal-install git-fmt
export PATH=$PATH:~/.cabal/bin

Usage

git-fmt itself just provides a way to select files in the git repository and pipe them through a pretty-printer. It also provides a dry-run mode that will show you which files need prettifying.

Configuration

Configuration is done through an .omnifmt.yaml file in the repository's top-level directory.

To show how, here's an example .omnifmt.yaml with 4 programs:

haskell:
    extensions: ["hs", "lhs"]
    command:    "stylish-haskell {{input}} > {{output}}"

javascript:
    extensions: ["js"]
    command:    "js-beautify -"

json:
    extensions: ["json"]
    command:    "json_pp"

ruby:
    extensions: ["rb"]
    command:    "ruby-beautify {{input}}"

That's all it takes! Each command declares how to read the input file and how to write to the output file. If the input variable is omitted, it is fed to the command through stdin. Likewise if the output variable is omitted it is read from stdout. The output file is used to compare whether the original input was pretty or ugly before writing to the original.

Extensions is pretty self explanatory, but if you use the same extension more than once then precedence goes to the first defined pretty-printer.

Examples

See the examples/ directory for some common pretty-printers and their corresponding omnifmt config. Just don't forget to actually call the config file .omnifmt.yaml!

NB: Be careful when using these examples, I have not tested the pretty-printers fully to check that they will not destroy your code by accident.