Semtex

Git presents all textual diffs in the same way. A change that could break your production system looks identical to a safe refactoring. Semtex splits up your diffs into those that affect the runtime behaviour and those that don't.

Segregating the changes makes the whole change easier to review. A change that is known not to impact the production system is trivial to review. A change that does impact runtime behaviour, should be kept small and focused.

• 📉 Minimise Risk by focusing your reviewer's attention on diffs that have the potential to introduce errors.
• 🏎️ Accelerate Code Reviews as it is easier to review something that you know won't impact the runtime behaviour.
• 🛠️ Enables Incremental Improvements to be made as they are spotted rather than waiting until after you have committed - there's a good chance you will forget! These changes are important to the next person who wants to understand this code.

Testing on a number of open-source projects indicates that you can expect over 25% of C# file changes to contain changes that do not alter the behaviour.[1]

Quick Start

Make your code reviewer's life easier

Run the following command to split your staged changes in two: one half containing changes that affect runtime behaviour, and another focused on improving code quality.

semtex split

To commit only those changes that effect the runtime behaviour of your application use:

semtex commit Behavioural <commit message>

To commit changes that focus on improving quality, run:

semtex commit Quality <commit message>

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Evaluate the Impact of a Commit

Generate a summary that highlights portions of an existing commit that impact runtime behaviour:

semtex check https://github.com/repo.git <commit>

To analyze multiple commits, you can specify a base:

semtex check https://github.com/repo.git <feature-branch> --base master

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Additional Commands

For a comprehensive list of all available commands, run:

semtex -h

How Semtex Works:

• Semtex harnesses Roslyn to interact with the C# compiler's internal representation of your codebase. This produces a simplified representation of the semantics of your program, allowing us to ignore portions of your codebase that don't affect the execution, such as comments and outlined constants.

• Semtex builds on top of Roslynator, which provides open-source code fixes for common code quality faults in C# codebases. Semtex processes all changes that won't affect the semantics of your code, making it easy to identify these simplifications.

• The behavioural equality function acts on a semantic representation of the program rather than the text itself. This enables Semtex to recognise chages such as the reordering of methods and renaming of local variables.

Getting Started

Try Semtex today by installing the tool with the following command:

dotnet tool install semtex --global

[1] Blog post coming soon with full details.