engineering: applying review cooments to CONTRIBUTING.md

Author: mcuadros

engineering/documents/CONTRIBUTING.md

@@ -2,45 +2,46 @@
 
 source{d} go-git project is [Apache 2.0 licensed](LICENSE) and accept
 contributions via GitHub pull requests.  This document outlines some of the
-conventions on development workflow, commit message formatting, contact points
+conventions on development workflow, commit message formatting, contact points,
 and other resources to make it easier to get your contribution accepted.
 
 ## Certificate of Origin
 
-By contributing to this project you agree to the Developer Certificate of
-Origin (DCO). This document was created by the Linux Kernel community and is a
+By contributing to this project you agree to the [Developer Certificate of
+Origin (DCO)](DCO). This document was created by the Linux Kernel community and is a
 simple statement that you, as a contributor, have the legal right to make the
-contribution. See the [DCO](DCO) file for details.
+contribution.
 
 ## Support Channels
 
-Whether you are a user or contributor, official support channels include:
+The official support channels, for both users and contributors, are:
 
-- GitHub [issues](https://github.com/src-d/go-git/issues/new)
-- Slack: #go-git room in the [source{d} Slack](http://sourced.tech/)
+- GitHub [issues](https://github.com/src-d/go-git/issues)*
+- Slack: #go-git room in the [source{d} Slack](https://join.slack.com/t/sourced-community/shared_invite/enQtMjc4Njk5MzEyNzM2LTFjNzY4NjEwZGEwMzRiNTM4MzRlMzQ4MmIzZjkwZmZlM2NjODUxZmJjNDI1OTcxNDAyMmZlNmFjODZlNTg0YWM)
 
-Before opening a new issue or submitting a new pull request, it's helpful to
+*Before opening a new issue or submitting a new pull request, it's helpful to
 search the project - it's likely that another user has already reported the
 issue you're facing, or it's a known issue that we're already aware of.
 
 
 ## How to Contribute
 
-PRs are the main and exclusive way to contribute to the official go-git project.
+Pull Requests (PRs) are the main and exclusive way to contribute to the official go-git project.
 In order for a PR to be accepted it needs to pass a list of requirements:
 
 - You should be able to run the same query using `git`. We don't accept features that are not implemented in the official git implementation.
-- The expected behavior must match the official git implementation.
+- The expected behavior must match the [official git implementation](https://github.com/git/git).
 - The actual behavior must be correctly explained with natural language and providing a minimum working example in Go that reproduces it.
-- In case a PR is submitted, it has to be written in idiomatic Go, formatted properly using gofmt, that compiles without warning and passes all the current tests.
+- All PRs must be written in idiomatic Go, formatted according to [gofmt](https://golang.org/cmd/gofmt/), and without any warnings from [go lint](https://github.com/golang/lint) nor [go vet](https://golang.org/cmd/vet/).
+They should in general include tests, and those shall pass.
 - If the PR is a bug fix, it has to include a new unit test that fails before the patch is merged.
 - If the PR is a new feature, it has to come with a suite of unit tests, that tests the new functionality.
-- In any case, all the PRs have to pass the personal evaluation of at least one of the maintainers of go-git.
+- In any case, all the PRs have to pass the personal evaluation of at least one of the [maintainers](MAINTAINERS) of go-git.
 
 
 ### Format of the commit message
 
-Every commit message should describe what changed, in which context:
+Every commit message should describe what was changed, under which context and, if applicable, the GitHub issue it relates to:
 
 ```
 plumbing: packp, Skip argument validations for unknown capabilities. Fixes #623