Add pre-commit support

[alexjurkiewicz]

This PR adds a file so that tslint can be used natively with pre-commit.

If this PR is accepted, I'll submit a PR to update the documentation on pre-commit's side too!

[vvakame]

Thank you for your contributions!
I first learned about the pre-commit project now 😉
I have a some questions.

[vvakame]

Why do you use system?
Is node more appropriate? http://pre-commit.com/#node

My suggestions, We should use project local tsfmt, not system wide tsfmt.
I think you have a two or more project about tsfmt using. There project should be able to update dependencies independently.

[alexjurkiewicz]

good point. I haven't used node language before, but it seems like tsfmt should be compatible as-is.

[vvakame]

Is this the regexp?
I want to use \.tsx?$.

[alexjurkiewicz]

done

[vvakame]

👀 palantir/tslint#2562

[vvakame]

I tried to use pre-commit, but I can't do it..
https://github.com/vvakame/typescript-formatter/tree/alexjurkiewicz-pre-commit
https://gist.github.com/vvakame/3ae719362d4de86b966ae6f79deb0d58

I have a question.
tsfmt & tslint projects are must be installed via npm.
Is pre-commit project can do that? I think that that project is not support it well...

[alexjurkiewicz]

Sorry for the error. I thought I understood pre-commit + node but I didn't 🙇 .

The solution is to add an additional_dependencies key to .pre-commit-hooks.yaml:

-   id:          tsfmt
    name:        TypeScript Formatter (tsfmt)
    description: TypeScript code auto-formatter.
    entry:       tsfmt --verify
    language:    node
    files:       \.tsx?$
    additional_dependencies: ['typescript-formatter', 'typescript']

You can also specify a certain version of dependencies like using npm/yarn:

additional_dependencies: ['typescript-formatter', 'typescript@2.2.2']

However, this will mean that there would need to be a new commit for each typescript version that changes typescript-formatter behaviour. Each update to the pre commit file could be recorded for users to use a certain version of typescript with. Example .pre-commit-hooks.yaml content:

# Use the following SHAs:
# * typescript 1.9: aaaaaaaa
# * typescript 2.0: bbbbbbb
# * typescript 2.2: cccccccc
-   repo: git@github.com:vvakame/typescript-formatter.git
    sha: <sha>
[...]

This is getting a bit complex, sorry. I think you wouldn't like this in your main repo, is that right?

What I can do instead is maintain a dedicated pre-commit-tsfmt repository, like jshint.

[alexjurkiewicz]

One possible additional complication. The additional_dependencies line should probably specify the typescript-formatter version.

[vvakame]

sorry for late reply.

I think you wouldn't like this in your main repo, is that right?
What I can do instead is maintain a dedicated pre-commit-tsfmt repository, like jshint.

sounds good! I recommended it.
I am not a user, so it would be better to maintain it by the people actually using it.