Update README.md

README.md

@@ -45,3 +45,74 @@ configs:
   - split: test
     path: data/test-*
 ---
+
+# Diff-XYZ
+
+Diff-XYZ contains 1,000 real-world code edits sampled and filtered from
+the [CommitPackFT](https://huggingface.co/datasets/bigcode/commitpackft) dataset.  
+Each example provides three components: the original file contents (`old_code`), the modified contents (`new_code`), and
+multiple diff representations (`udiff`, `udiff-h`, `udiff-l`, and `search-replace`).
+
+These formats enable evaluation of LLM capabilities on three code editing tasks:
+
+- **Apply**: Given old code and diff, generate new code
+- **Anti-Apply**: Given new code and diff, generate old code
+- **Diff-Generation**: Given old and new code, generate the diff
+
+## How it's built
+
+Examples were systematically filtered from CommitPackFT to ensure high quality:
+
+- **Scope**: Single-file changes only, excluding binary files, vendor directories, and generated code
+- **Quality**: Removed trivial changes (whitespace-only) and likely test files
+- **Size**: Required 40+ lines in at least one version of the code (old or new); excluded very large files (1000+ lines)
+- **Sampling**:
+    - Target 50/50 split between single-hunk and multi-hunk edits (hunks counted via `@@` markers in the unified diff).
+    - Within each hunk group, stratify by change size (lines added + removed) using the 40th/80th percentiles of that
+      group, targeting ≈40% small, 40% medium, 20% large.
+    - Cap examples to ≤5 per repository per language.
+
+## Dataset Statistics
+
+- **Total examples:** 1,000
+- **Languages:** Python (200), JavaScript (200), Java (200), Kotlin (200), Rust (200)
+
+**Hunks:**
+
+- **1 hunk:** 500 (50.0%)
+- **2+ hunks:** 500 (50.0%)
+
+**Change size (added + removed), stratified within hunk groups:**
+
+- **Small** (≤40th pct): 424 (42.4%)
+- **Medium** (40th–80th): 388 (38.8%)
+- **Large** (>80th): 188 (18.8%)
+
+**Change type:**
+
+- **Mixed** (additions + deletions): 815 (81.5%)
+- **Add-only:** 163 (16.3%)
+- **Delete-only:** 22 (2.2%)
+
+**Repository diversity:** 891 unique repositories.
+
+## Schema
+
+| Field            | Type   | Description                                                            |
+|------------------|--------|------------------------------------------------------------------------|
+| `repo`           | string | Repository identifier (e.g., "owner/name")                             |
+| `commit`         | string | Commit SHA that produced the change                                    |
+| `path`           | string | File path relative to repo root                                        |
+| `lang`           | string | One of: `python`, `javascript`, `java`, `kotlin`, `rust`               |
+| `license`        | string | SPDX license identifier of the repo                                    |
+| `message`        | string | Original commit message                                                |
+| `old_code`       | string | Complete file contents before change                                   |
+| `new_code`       | string | Complete file contents after change                                    |
+| `n_added`        | int    | # of `+` lines (excluding headers)                                     |
+| `n_removed`      | int    | # of `-` lines (excluding headers)                                     |
+| `n_hunks`        | int    | # of `@@` (hunk) sections                                              |
+| `change_kind`    | string | `add_only`, `del_only`, or `mixed`                                     |
+| `udiff`          | string | Standard unified diff (1-line context, numeric hunk headers)           |
+| `udiff-h`        | string | Unified diff with relaxed hunk headers written as `@@ ... @@`          |
+| `udiff-l`        | string | Unified diff with explicit line markers: `ADD`, `DEL`, and `CON`       |
+| `search-replace` | string | Search/replace representation: pairs of `SEARCH`/`REPLACE` edit blocks |