{"slug": "create-a-side-by-side-html-word-diff-between-two-git-revisions-generated-with-6", "title": "Create a side-by-side HTML word diff between two Git revisions (generated with gpt-6-luna)", "summary": "A developer published a Python script that generates a side-by-side HTML word diff between two Git revisions, parsing git's word-diff markers to render deletions and additions in separate columns. The tool wraps diff output in a dark-themed, sticky-header HTML table with per-file and per-hunk headings, and is run as a self-contained uv script with argparse-based pathspec filtering.", "body_md": "| | #!/usr/bin/env -S uv run --script | \n| | \"\"\"Create a side-by-side HTML word diff between two Git revisions.\"\"\" | \n| | import argparse | \n| | from html import escape | \n| | from pathlib import Path | \n| | import re | \n| | import subprocess | \n| | import sys | \n| | MARKER = re.compile(r\"(\\[-.*?-\\]\\|\\{\\+.*?\\+\\})\") | \n| | def parse_paths(value: str \\| None) -> list[str]: | \n| | \"\"\"Parse a comma-separated list of paths for the Git pathspec.\"\"\" | \n| | if value is None: | \n| | return [] | \n| | paths = [path.strip() for path in value.split(\",\")] | \n| | if any(not path for path in paths): | \n| | raise argparse.ArgumentTypeError(\"file lists must not contain empty entries\") | \n| | return paths | \n| | def render_side(line: str, side: str) -> tuple[str, str]: | \n| | \"\"\"Render one diff line for the original or new side.\"\"\" | \n| | rendered: list[str] = [] | \n| | has_deletion = has_addition = has_context = False | \n| | for part in MARKER.split(line): | \n| | if not part: | \n| | continue | \n| | if part.startswith(\"[-\") and part.endswith(\"-]\"): | \n| | has_deletion = True | \n| | if side == \"old\": | \n| | rendered.append(f'{escape(part[2:-2])}') | \n| | elif part.startswith(\"{+\") and part.endswith(\"+}\"): | \n| | has_addition = True | \n| | if side == \"new\": | \n| | rendered.append(f'{escape(part[2:-2])}') | \n| | else: | \n| | has_context \\|= bool(part.strip()) | \n| | rendered.append(escape(part)) | \n| | cell_class = \"\" | \n| | if side == \"old\" and has_deletion and not has_addition and not has_context: | \n| | cell_class = ' class=\"whole-del\"' | \n| | elif side == \"new\" and has_addition and not has_deletion and not has_context: | \n| | cell_class = ' class=\"whole-add\"' | \n| | return \"\".join(rendered) or \"\", cell_class | \n| | def diff_to_html(diff: str, old: str, new: str) -> str: | \n| | rows: list[str] = [] | \n| | for line in diff.splitlines(): | \n| | if line.startswith(\"diff --git \"): | \n| | heading = escape(line[len(\"diff --git \") :]) | \n| | rows.append(f'| {heading} |
|---|
') | \n| | elif line.startswith(\"@@ \"): | \n| | rows.append(f'| {escape(line)} |
|---|
') | \n| | elif line.startswith((\"index \", \"--- \", \"+++ \")): | \n| | rows.append(f'| {escape(line)} |
') | \n| | else: | \n| | original, original_class = render_side(line, \"old\") | \n| | updated, updated_class = render_side(line, \"new\") | \n| | rows.append( | \n| | f\"{original}\" | \n| | f\"{updated}|
\" | \n| | ) | \n| | return f''' | \n| | | \n| | | \n| | | \n| | | \n| | Diff: {escape(old)} → {escape(new)} | \n| | | \n| | | \n| | | \n| | Original: {escape(old)}
New: {escape(new)}
| \n| | | \n| | {chr(10).join(rows)} | \n| |