GitEvo: Code Evolution Analysis for Git Repositories
This paper presents GitEvo, a multi-language and extensible tool that integrates Git-level and code-level analysis to support code evolution studies for practitioners, researchers, and educators.
Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Imagine you have a giant, living library of software code. Every time a programmer makes a change, they add a new page to a book, but they also keep a perfect diary of every single edit, who made it, and when. This diary is called a Git repository.
For a long time, we had two different ways to look at this library:
- The Librarian's View: Tools that could tell you how many pages were added, who wrote them, and when the book was updated. But they couldn't read the actual words inside the pages.
- The Editor's View: Tools that could read the words, count the sentences, and analyze the grammar of a single page. But they couldn't see the history; they just looked at one snapshot in time.
GitEvo is a new tool that acts like a super-intelligent time-traveling editor. It combines both views, allowing you to watch how the "words" of the code change over time, not just the number of pages.
Here is how it works, using simple analogies:
1. The "Time-Traveling Camera"
Think of GitEvo as a camera that doesn't just take a photo of a building; it takes a photo of the building every day for ten years and stitches them together into a movie.
- The Old Way: You could count how many bricks were added each year (Git-level), or you could analyze the architectural style of the building on a single day (Code-level).
- The GitEvo Way: It watches the building evolve. It can tell you, "In 2020, the architects started using more glass windows (a specific coding pattern), and by 2024, the whole front wall was made of glass." It connects the history of the project with the details of the code.
2. The "Universal Translator"
One of the biggest headaches in software is that different languages (Python, Java, JavaScript) usually require different tools to read them. It's like needing a French dictionary for French books and a Spanish dictionary for Spanish books, with no way to compare them easily.
GitEvo is like a universal translator that speaks all these languages at once.
- It uses a powerful "grammar engine" (called Tree-sitter) that can read Python, JavaScript, TypeScript, and Java.
- Instead of writing a new script for every language, a user writes one script in Python, and GitEvo translates that script to understand the code in any of those four languages. It's like having one set of binoculars that works for birds, fish, and mammals.
3. How You Use It (The "Recipe Book")
The paper explains two ways to use GitEvo:
- The "Off-the-Shelf" Meal (Command Line): If you just want to see a quick report, you can type a simple command, like asking a chef to "make a salad." GitEvo instantly generates a report showing how the code grew, how many tests were added, or how complex the code became over time. It gives you a ready-made chart or a spreadsheet.
- The "Custom Recipe" (API): If you are a researcher or a curious developer, you can write your own "recipe." You can tell GitEvo, "I want to count how many times the developers used a specific type of loop" or "I want to track how many 'mock' tests (fake data tests) were added over the last five years." GitEvo then runs this custom recipe across the entire history of the project and draws a graph for you.
4. What People Are Doing With It
The paper highlights three main groups using this tool:
- Researchers (The Scientists): They used GitEvo to study over 1.2 million changes in code. For example, they tracked how often developers started using "mocking" (a testing technique) across different languages, or how the usage of specific Python features (like "lambdas") changed over a decade.
- Practitioners (The Builders): Developers at companies like FastAPI used it to look back at their own work. One developer said it was great to "step back and see the work we've done." It helps them visualize trends, like "Are we writing more tests?" or "Is our code getting more complex?"
- Educators (The Teachers): In a university class, over 90 students used GitEvo to explore real-world software. Instead of just reading about how software changes, they could see it happen. They discovered things like, "Oh, this project stopped using one type of variable and switched to another," helping them understand real engineering decisions.
The Bottom Line
GitEvo is a tool that bridges the gap between history (what happened in the repository) and content (what the code actually says). It allows anyone to ask, "How did this software evolve?" and get a clear, visual answer, regardless of whether the code was written in Python, Java, or JavaScript. It turns a messy history of code changes into a clear story of growth and change.
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