Оvercommit - convenient Git hook manager

Voldemar Duletskiy, Ruby developer, Evrone, Moscow Ruby Meet-up 6 report
01 August 2017   2285

Dynamic, open source programming language with a focus on simplicity and productivity, it has an elegant syntax that is natural to read and easy to write.

Hello Ruby fans! Today we will talk about Overcommit - the convenient management of git-hooks.

Imagine that you have a small project with a micro-team of three or four people, including the manager. Deadline is near, but you cannot lower the quality of the code. You don't wanna use CI and there are no extra money for it.

What is hooks and where are they located?

It is the scripts that are executed at certain event. You can view all existing hooks by running the following command:

ls -la .git/hooks

You will see this listing:

-rwxr-xr-x   1 voldemar  staff  3755 28 Jun 16:39 commit-msg
-rwxr-xr-x   1 voldemar  staff  3755 28 июн 16:39 overcommit-hook
-rwxr-xr-x   1 voldemar  staff  3755 28 Jun 16:39 post-checkout
-rwxr-xr-x   1 voldemar  staff  3755 28 Jun 16:39 post-commit
-rwxr-xr-x   1 voldemar  staff  3755 28 Jun 16:39 post-merge
-rwxr-xr-x   1 voldemar  staff  3755 28 Jun 16:39 post-rewrite
-rwxr-xr-x   1 voldemar  staff  3755 28 Jun 16:39 pre-commit
-rwxr-xr-x   1 voldemar  staff   673  2 Jun 14:37 pre-commit.sh
-rwxr-xr-x   1 voldemar  staff  3755 28 Jun 16:39 pre-push
-rwxr-xr-x   1 voldemar  staff  3755 28 Jun 16:39 pre-rebase

Hook is an executable file, which can content anything, including the Ruby code.

Why it is cool?

  • You can put linters like rubocop to the pre-commit hooks. It will not allow you to commit substandard code
  • You can hang up rspec to the pre-push hooks, and if the tests are dropped - cancel code sending
  • If you are already actively using hooks - you don't need to drag them from one repository to another, they all lie in .ovecommit.yml in a convenient format

Ruby static code analyzer, based on the community Ruby style guide

If you suffer from dispersion and you are sick of messages from your CI that tests have dropped again, or the ruby-cop found a million syntactic violations (or your colleagues in the code-review process). If you are an experienced developer, a good set of hooks seriously discourages young developers and reduces your code-review time. 



gem 'overcommit'

Execude from the consol:

bundle exec overcommit --install

 Now let's edit .overcommit.yml file

    enabled: true
    command: ['bin/bundle', 'exec', 'rubocop', '-R']
    on_warn: fail
    enabled: true
    command: ['bin/bundle', 'exec', 'haml-lint', 'app/views/']
    on_warn: fail
    enabled: true
    command: ['bin/bundle', 'exec', 'scss-lint']
    include: 'app/assets/**/*.scss'
    on_warn: fail

    enabled: true

We can see here that the launch of the rubocop scripts is describled in nice forman. haml-linter, sccs-linter and tests runs just before the commit.

In order to enforce hook running this should be executed:

bundle exec overcommit -R

Now, with every attempt to commit something, checks will be performed firstly.


Underwater rocks

If there are a lot of tests or they are dropping randomly - if you already have a habit to brew coffee while test runs, it's better to chop the hook responsible for running the tests. If they fall randomly - fix the tests at last, damn it.

Integration with Rubymine - I have serious problems with the integration of Overcommit and Rubymine

Continuous Integration

The practice of merging all developer working copies to a shared mainline several times a day

Overcommit and CI integration - if you still decide to connect CI, then most likely it already provides validation for the code. Often, their rules don't match and you have to adjust the settings, for example Rubocop under CI, or vice versa.

You can skip hooks by running git commit --no-verify


Overcommit is an excellent utility for maintaining a project in good shape for small teams. It will allow you not to grab your head every time after creating a pool of the requester with exclamations "Damn, I forgot to use rubocop again!" or "Damn, all the tests fell!".

New Bug to be Discovered in Ruby

Deserialization issue in Ruby was discovered by Elttam from Australia
12 November 2018   107

The problem of serialization and deserialization of objects has reached Ruby. Bug found by the experts from the company Elttam, Australia.

Serialization in programming is the translation of a data structure into any other format more convenient for storage. The inverse operation is the operation of deserialization - the restoration of the initial state of the data structure from the bit sequence. The possibility of this is built into Ruby and, as it turned out, it allows attackers to use the native language mechanisms to carry out their attacks.

Elttam researchers have added a proof-of-concept exploit to the report that implements it. The problem is that these mechanisms are built into the language itself, namely in versions from 2.0 to 2.5. It is also assumed that it is possible to refine the attack methods for older versions. In addition, alternative implementations of Ruby called JRuby and Rubinius can potentially have similar problems.

Vulnerabilities of serialization and deserialization of objects exist in other languages. In 2015, they were found in the FoxGlove Security for Java library. In 2017, a similar problem was discovered in .NET libraries, and in 2018, in PHP. In the latter case, it affects the WordPress engine. Often problems are solved by the release of patches, although bugs are often difficult to detect. At the same time, it should be understood that the serialization and deserialization of data in itself weakens their protection.