Update contributing guidelines

CONTRIBUTING.md

@@ -1,15 +1,109 @@
 # Contributing
 
-Before contributing, please read [our code style](https://github.com/teloxide/teloxide/blob/master/CODE_STYLE.md) and [the license](https://github.com/teloxide/teloxide/blob/master/LICENSE).
+Before contributing, please read [our code style](./CODE_STYLE.md) and [the license](./LICENSE).
 
-To change the source code, fork the `master` branch of this repository and work inside your own branch. Then send us a PR into `master` branch and wait for the CI to check everything. However, you'd better check changes first locally:
+> **Note**
+>
+> These contributing instructions might not be fully up-to-date or complete.
+> However, they should be a good starting point.
+>
+> If you find inaccuracies / missing things, please expand this or contact us.
 
-```
-cargo clippy --all --all-features --all-targets
-cargo test --all
-RUSTDOCFLAGS="--cfg docsrs" cargo doc --open --all-features
-# Using nightly rustfmt
-cargo +nightly fmt --all -- --check
+## Reporting bugs, questions, feature requests
+
+To report a bug or suggest new functionality go to [issues](https://github.com/teloxide/teloxide/issues).
+Try to make MRE (**M**inimal **R**eproducible **E**xample) and specify your teloxide version to let others help you.
+
+If you want to ask a question, you can either
+- Open a new [github discussion](https://github.com/teloxide/teloxide/discussions), or
+- Write to our telegram group ([eng](https://t.me/teloxide), [ru](https://t.me/teloxide_ru))
+
+## Code
+
+### Git
+
+To change the source code, you need a local copy of it.
+Fork the `master` branch of this repository via github and clone your fork locally.
+
+When working on a new thing, create a new branch with `git switch -c my-branch-name` (or other commands that work with branches).
+This way it will be easier to manage when you want to do other things.
+
+When your changes are ready, you can open a github pull request.
+
+If your branch has conflicts with master please resolve them by doing something like this:
+```shell
+# Temporary switch to master branch
+git switch master
+
+# Pull changes from the upstream.
+# You may need to use something different from "origin",
+# depending on how you setup your remotes.
+git pull origin master
+
+# Switch back to your feature branch
+git switch -
+
+# Move your changes on top of changes in master branch.
+git rebase master
+
+# Here you'll need to resolve the conflicts,
+# git commands will print some guidance.
+
+# Once conflicts are resolved,
+# forcefully push the changes to your fork
+git push --force-with-lease
 ```
 
-To report a bug, suggest new functionality, or ask a question, go to [Issues](https://github.com/teloxide/teloxide/issues). Try to make MRE (**M**inimal **R**eproducible **E**xample) and specify your teloxide version to let others help you.
+### Testing
+
+When you open a PR it will be tested in CI.
+We recommend you test the PR before opening it:
+
+```shell
+# Formatting (use `-- --check` if you only want to check)
+cargo fmt --all
+
+# Build
+cargo build --features "full nightly"
+
+# Run linter
+cargo clippy --all-targets --features "full nightly"
+
+# Running tests
+cargo test --features "full nightly"
+
+# Documentation (use --open if you want to open it in a browser)
+# (note the -s, `docs` is an alias to pass some additional flags to `rustdoc`)
+cargo docs
+```
+
+## Teloxide bot
+
+Teloxide uses @teloxidebot as a helper to manage PRs and issues.
+It's based on triagebot developed by rustc developers which docs can be found [here](https://forge.rust-lang.org/triagebot/index.html).
+
+We'll describe here a few most used @teloxidebot's features, but we still recommend you read the docs.
+
+### PR status tracking
+
+Teloxide uses `S-*` labels (mainly https://github.com/teloxide/teloxide/labels/S-waiting-on-author and https://github.com/teloxide/teloxide/labels/S-waiting-on-review) to track the status of pull requests.
+
+You can change the status with `@teloxidebot review` and `@teloxidebot ready` (set the status to https://github.com/teloxide/teloxide/labels/S-waiting-on-review) or `@teloxidebot author` (sets the status to https://github.com/teloxide/teloxide/labels/S-waiting-on-author).
+
+Requesting a review from PR's assignee via github ui will also change the status of the PR to waiting on review.
+Similarly, submitting a review that requests changes will change the status of the PR to waiting on author.
+
+There is also https://github.com/teloxide/teloxide/labels/S-blocked which can be set with `@teloxidebot blocked`.
+
+Please note that your PR won't be reviewed unless it's waiting for review :)
+
+### Labels
+
+Normally github only allows privileged users to change labels.
+@teloxidebot allows anyone to add or remove certain [labels](https://github.com/teloxide/teloxide/labels/) with `@teloxidebot label +additional_label -removed_label`.
+See more in the [documentation](https://forge.rust-lang.org/triagebot/index.html).
+
+### PR assignment
+
+When a PR is created @teloxidebot will automatically assign one of the maintainers to it.
+If you want to override this assignment, use `r? @ReviewerUsername`.