docs: add contributing guidelines

Co-authored-by: Hocuri <hocuri@gmx.de>

.github/mergeable.yml

@@ -5,11 +5,11 @@ mergeable:
     validate:
       - do: title
         begins_with:
-          match: ['feat', 'fix', 'api', 'refactor', 'perf', 'test', 'style', 'chore', 'cargo', 'build', 'ci']
+          match: ['feat', 'fix', 'api', 'refactor', 'perf', 'test', 'style', 'chore', 'cargo', 'build', 'ci', 'docs']
 
     fail:
       - do: checks
         status: "action_required"
         payload:
           title: PR title should follow conventional commits
-          summary: "PR title should follow https://conventionalcommits.org. E.g. start with 'feat:' (for Features / Changes), 'fix:' (for Fixes), 'api:' (for API-Changes), 'api!:' (for breaking API-Changes) 'refactor:' (for Refactor), 'perf:' (for Performance), 'test:' (for Tests), 'style:' (for Styling), 'chore:' (for Miscellaneous Tasks)"
+          summary: "PR title should follow https://conventionalcommits.org. See https://github.com/deltachat/deltachat-core-rust/blob/master/CONTRIBUTING.md for details."

CONTRIBUTING.md

@@ -0,0 +1,70 @@
+# Contributing guidelines
+
+## Reporting bugs
+
+If you found a bug, [report it on GitHub](https://github.com/deltachat/deltachat-core-rust/issues).
+If the bug you found is specific to
+[Android](https://github.com/deltachat/deltachat-android/issues),
+[iOS](https://github.com/deltachat/deltachat-ios/issues) or
+[Desktop](https://github.com/deltachat/deltachat-desktop/issues),
+report it to the corresponding repository.
+
+## Proposing features
+
+If you have a feature request, create a new topic on the [forum](https://support.delta.chat/).
+
+## Contributing code
+
+If you want to contribute a code, [open a pull request](https://github.com/deltachat/deltachat-core-rust/pulls).
+
+You can find the list of good first issues
+and a link to this guide
+on the contributing page: <https://github.com/deltachat/deltachat-core-rust/contribute>
+
+### Coding conventions
+
+We format the code using `rustfmt`. Run `cargo fmt` prior to committing the code.
+Run `scripts/clippy.sh` to check the code for common mistakes with [Clippy].
+
+Commit messages follow the [Conventional Commits] notation.
+We use [git-cliff] to generate the changelog from commit messages before the release.
+
+With **`git cliff --unreleased`**, you can check how the changelog entry for your commit will look.
+
+The following prefix types are used:
+- `feat`: Features, e.g. "feat: Pause IO for BackupProvider". If you are unsure what's the category of your commit, you can often just use `feat`.
+- `fix`: Bug fixes, e.g. "fix: delete `smtp` rows when message sending is cancelled"
+- `api`: API changes, e.g. "api(rust): add `get_msg_read_receipts(context, msg_id)`"
+- `refactor`: Refactorings, e.g. "refactor: iterate over `msg_ids` without `.iter()`"
+- `perf`: Performance improvements, e.g. "perf: improve SQLite performance with `PRAGMA synchronous=normal`"
+- `test`: Test changes and improvements to the testing framework.
+- `build`: Build system and tool configuration changes, e.g. "build(git-cliff): put "ci" commits into "CI" section of changelog"
+- `ci`: CI configuration changes, e.g. "ci: limit artifact retention time for `libdeltachat.a` to 1 day"
+- `docs`: Documentation changes, e.g. "docs: add contributing guidelines"
+- `chore`: miscellaneous tasks, e.g. "chore: add `.DS_Store` to `.gitignore`"
+
+Release preparation commits are marked as "chore(release): prepare for vX.Y.Z".
+
+#### Breaking Changes
+
+Use a `!` to mark breaking changes, e.g. "api!: Remove `dc_chat_can_send`".
+
+Alternatively, breaking changes can go into the commit description, e.g.:
+
+```
+fix: Fix race condition and db corruption when a message was received during backup
+
+BREAKING CHANGE: You have to call `dc_stop_io()`/`dc_start_io()` before/after `dc_imex(DC_IMEX_EXPORT_BACKUP)`
+```
+
+#### Multiple Changes in one PR
+
+If you have multiple changes in one PR, create multiple conventional commits, and then do a rebase merge. Otherwise, you should usually do a squash merge.
+
+[Clippy]: https://doc.rust-lang.org/clippy/
+[Conventional Commits]: https://www.conventionalcommits.org/
+[git-cliff]: https://git-cliff.org/
+
+## Other ways to contribute
+
+For other ways to contribute, refer to the [website](https://delta.chat/en/contribute).