hew

A fast, review-first terminal patch viewer, in Rust.

hew reads a unified diff and opens it in an interactive review UI where you can attach GitHub-PR-style threaded comments. Source selection (working tree, revs, two files) is delegated to git — you just pipe a diff in.

hew = to cut/shape a block with an axe. Same "chunk/block" lineage as a diff hunk. Three letters, fast to type. Inspired by hunk, rebuilt from zero as a native single binary.

Install

cargo install --path .
# or
cargo build --release   # → target/release/hew

Usage

hew consumes a unified patch and nothing else — from a file, or stdin:

hew change.patch                 # review a patch file
git diff HEAD | hew              # review the working tree (piped)
git show <rev> | hew             # review a commit
git diff <a> <b> | hew           # compare two refs
hew - < change.patch             # explicit stdin

hew change.patch --json          # print the parsed changeset as JSON, no TUI

Load review comments from a sidecar JSON file:

hew change.patch --comments review.json

Options

Keys

Comments live in memory only — nothing is written back to the patch or to disk.

Comment sidecar format

{
  "threads": [
    {
      "file": "src/main.rs",
      "side": "new",
      "range": { "start": 18, "end": 22 },
      "resolved": false,
      "comments": [
        { "author": "agent", "body": "This match arm is unreachable." },
        { "author": "you",   "body": "Good catch." }
      ]
    }
  ]
}

• side: "new" (added/context, RIGHT) or "old" (removed, LEFT)
• range: a single line uses start == end
• comments[0] is the thread root; the rest are replies
• author, resolved, id, created_at are optional (sensible defaults)

A bare [ ...threads... ] array is also accepted.

Examples

Real {patch + comments} from public PRs live in examples/:

hew examples/misskey-ja.patch   --comments examples/misskey-ja.comments.json
hew examples/rust-long-en.patch --comments examples/rust-long-en.comments.json

See examples/README.md for how to fetch more.

Design & roadmap

hew is intentionally a read-only viewer: no persistence, no GitHub/network integration, no patch apply/edit/merge, no structural (AST) diff. Today it is a single-pane unified viewer with threaded comments.

Planned: split/stack layouts and a file sidebar, syntax highlighting (syntect → tree-sitter), --watch reload, and a loopback session server so an agent/CLI can drive a running TUI.

Note: hew parses plain unified diffs, not git format-patch mailbox output (gh pr diff --patch). Use a .diff/git diff stream instead.