docs: enhance contributing guidelines

docs: add git-branching diagram

- add git workflow instructions
- add branching strategy
- add instruction for git squashing

docs: don’t scare off potential contributors

because:
- having to open a GitHub issue first every time could prevent
contributors to make the effort of submitting their thoughts

this commit:
- removes the respective paragraph in the `CONTRIBUTING.md`

docs: change GitHub issue template

because:
- we want a consistent formatting with our commit guidelines

this commit:
- changes the `.github` template files accordingly and
- adjusts the docs in the `CONTRIBUTING.md` file

style: improve wording

docs: clarify prefered way to offer help

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,7 +1,7 @@
 ---
 name: Bug report
 about: Create a report to help us improve
-title: "[Bug] <enter name of bug here>"
+title: "bug: <enter name of bug here>"
 labels: bug
 assignees: ''
 ---

.github/ISSUE_TEMPLATE/feature_request.md

@@ -1,7 +1,7 @@
 ---
 name: Feature request
 about: Suggest an idea for this project
-title: "[Feature] <enter name of new feature here>"
+title: "feat: <enter name of new feature here>"
 labels: feature
 assignees: ''
 ---

.github/ISSUE_TEMPLATE/improvement.md

@@ -1,7 +1,7 @@
 ---
 name: Improvement
 about: Tell us what can be done better
-title: "[Improvement] <enter name of improvement here>"
+title: "improvement: <enter name of improvement here>"
 labels: improvement
 assignees: ''
 ---

.github/ISSUE_TEMPLATE/question.md

@@ -1,7 +1,7 @@
 ---
 name: Question
 about: Ask about FluidMS and what might be unclear in its usage
-title: "[Question] <enter your question here>"
+title: "question: <enter your question here>"
 labels: question
 assignees: ''
 ---

CONTRIBUTING.md

@@ -2,7 +2,50 @@
 
 This document provides a collection of rules and guidelines that need to be adhered to when working with or contributing to FluidMS.
 
-## Commit guidelines
+## Git workflow
+
+### Creating a GitHub issue
+
+For issues, please adhere to the following formatting of the issue title:
+
+```
+<type>: <description of the issue>
+```
+
+`<type>` can be one of the following:
+
+- `bug`
+- `feat`
+- `improvement`
+- `question`
+
+**Example:**
+
+```
+feat: add new testing tool
+```
+
+### Branching strategy
+
+Any work is performed on dedicated feature branches. This work is lead back to our `develop` base branch via pull requests. The `master` branch is our release and stable branch.
+
+![Diagram showing our Git branching strategy](git-branching.png)
+
+If you create a new branch, stick to the following naming convention:
+
+```
+<branch-type>/<GitHub-issue-number>/<branch-title>
+```
+
+`<branch-type>` can be any type that is also [allowed for commit types](#user-content-commit-guidelines):
+
+**Example:**
+
+```
+ci/12/travis-ci-integration
+```
+
+### Commit guidelines
 
 For our commit guidelines, we are using [Conventional Commits](https://www.conventionalcommits.org/). Please strictly adhere to these conventions.
 
@@ -19,3 +62,42 @@ Allowed types:
 - **test**: Adding missing tests or correcting existing tests
 
 _(based on [Angular contribution guidelines](https://github.com/angular/angular/blob/22b96b9/CONTRIBUTING.md#type))_
+
+#### Reference the GitHub issue
+
+To get a good paper trail and trace back any commits to their respective discussions, we reference each commit with the GitHub issue number that the commit is for. For that, put the issue number in parentheses with a hash prefix at the end of the commit description:
+
+```
+<type>[optional scope]: <description> (#<issue number>)
+```
+
+[Example:](https://github.com/csshugs/FluidMS/commit/6d6fe3c362907c6c0e07896c7ba4785d5d0b3f1d)
+```
+fix: webserver not serving `index.html` on baseUrl (#13)
+```
+
+#### Give context to your commits
+
+To be able to identify the **WHY** behind a commit at a later point in time, we use the following template for our commit body:
+
+```
+<type>[optional scope]: <description> (#<issue number>)
+
+because:
+- [relevant context]
+- [why you decided to change things]
+- [reason you’re doing it now]
+
+this commit:
+- [does X]
+- [does Y]
+- [does Z]
+```
+
+— _[Source](https://twitter.com/r00k/status/1175100703829909505)_
+
+### Squash your commits
+
+When a pull request is approved, all the commits need to be [squashed](https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History#_squashing) in a meaningful manner before the pull request is merged. That is, combining those commits that form a complete feature into **one commit**. That doesn’t necessarily mean that all the commits of every pull request should ever result in one single commit! For example, if a pull request provides a new feature but alongside this new feature, a bug was fixed, too, this would result in two sqashed commits: One for the feature and one for the bugfix. The aim of this practice is to produce a sensible fragmentation of commits so we can later automatically create our changelog from these commits.
+
+If you feel unsure about this process, just ping **[@fuhlig](https://github.com/fuhlig)** or **[@csshugs](https://github.com/csshugs)** in the comments of the pull request to request help. We’d love to do the squashing for you!

git-branching.drawio

@@ -0,0 +1 @@
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