SZZ Bug Identifier

SZZ (Śliwerski, Zimmermann, Zeller, 2005) answers: given a bug-fix commit, which earlier commit introduced the bug? It works by blaming the lines the fix touched.

The algorithm — classic SZZ

1. Identify the fix commit. Usually via a link to an issue tracker (Fixes #1234, BUG-567) or a message keyword (fix, bug, patch).
2. Extract the deleted/modified lines. In the fix's diff, every line removed or changed is a line that was (potentially) buggy.
3. Blame each of those lines. git blame <fix>^ -- <file> on each modified line to find the commit that last touched it before the fix.
4. Those blamed commits are bug-introducing candidates.

That's the whole algorithm. The rest is noise filtering.

Noise filters — classic SZZ's known weaknesses