GitWhisper – CLI that explains why your code changed, not just what

#programming #rust #hn #ai

The problem

git log tells you what changed. It never tells you why.
Every senior engineer has spent hours reading through 50 commits
trying to understand a decision made 3 months ago by someone
who left the company.

What GitWhisper does

It installs a post-commit hook that silently captures developer
context at commit time — branch name, recent terminal commands,
IDE state, and the full diff — and stores it as JSON inside
.git/gitwhisper/.json.

When you run:

gitwhisper explain src/auth.rs

It loads the full commit history for that file, pulls the captured
context for each commit, compresses everything into a 12k char
prompt budget, and asks Gemini or a local Ollama model to explain
why the file evolved the way it did.

Why Rust

Single binary. No runtime. Drop it into any repo without asking
teammates to install anything. Cold start is ~12ms.

Interesting engineering problems

The context optimizer was the hardest part. Naively passing full
history blows every model's context window. I ended up scoring
each commit by recency + file overlap + diff size then truncating
greedily until under budget.

Other commands that are useful day-to-day:

gitwhisper owners src/        # contribution-weighted ownership

gitwhisper security src/      # risky change pattern scan


gitwhisper bug-predict src/   # files statistically likely to have bugs

gitwhisper knowledge-risk src/ # bus factor analysis

gitwhisper dashboard          # web dashboard at :7878

Current rough edges

Terminal output is still plain println — colored crate is wired up in Cargo.toml but not applied yet
Dashboard is single-threaded TCP, blocks on one connection
Diff analysis is heuristic, no tree-sitter yet