Restore Markdown formatting in fmt/fmt-check and pin prettier (closes #19)

script/fmt and script/fmt-check now run gofmt for Go and prettier for
Markdown; fmt-check reports each independently. prettier is pinned at
3.8.1 by package.json/yarn.lock (integrity hash); .prettierrc and
.prettierignore are the house settings copied from the prompts repo.
script/bootstrap installs node and yarn from the host package manager
and runs `yarn install --frozen-lockfile`.

The Markdown check runs in CI via the Dockerfile build stage, where
bootstrap provides prettier; it is removed from the lint stage because
the golangci-lint image has no node. JS manifests are copied before
bootstrap so the yarn layer caches, and node_modules is dockerignored.

node is an unpinned host runtime like git/make/go: nvm's glibc node does
not run on the musl/Alpine build image, so the canonical nvm route is
not usable here; prettier is the hash-pinned formatter. The wholesale
Markdown reformat follows in the next commit.

Model: opus-4-8

.dockerignore

@@ -3,6 +3,7 @@
 .DS_Store
 sfdupes
 files.dat
+node_modules
 *.log
 *.out
 *.test

.prettierignore

@@ -0,0 +1,2 @@
+node_modules/
+yarn.lock

.prettierrc

@@ -0,0 +1,4 @@
+{
+    "tabWidth": 4,
+    "proseWrap": "always"
+}

Dockerfile

@@ -27,9 +27,12 @@ ARG CHECK_EPOCH
 # target now runs `docker build -f Dockerfile.lint`, and a docker build
 # cannot run a docker build: routing the gate through make would mean
 # nesting docker inside this image. Same reason `make check` is gone
-# from the build stage below. `make fmt-check` stays as it is — it is a
-# gate, not the aggregate, and it shells out to nothing.
-RUN echo "gate fmt-check, epoch ${CHECK_EPOCH}" && make fmt-check
+# from the build stage below.
+#
+# `make fmt-check` is not run in this stage: it now also runs prettier
+# over Markdown, and this golangci-lint image has no node. The gate runs
+# in the build stage below, where script/bootstrap installs node and
+# prettier.
 
 # The FROM above and the one in Dockerfile.lint pin the same linter
 # twice, and nothing else keeps them in sync; this fails the build when
@@ -77,10 +80,12 @@ COPY --from=lint /src/go.sum /dev/null
 # rather than duplicating the installs inline. Only script/ and the
 # dependency manifests are copied first, nothing else, so this layer
 # stays cached until the scripts or the dependencies change — bootstrap
-# ends in `go mod download`, which is why there is no separate
-# invocation of it here.
+# runs `go mod download` and `yarn install`, which is why there is no
+# separate invocation of either here. The JS manifests (package.json,
+# yarn.lock) are copied too so the yarn install layer caches alongside
+# the Go one.
 COPY script/ script/
-COPY go.mod go.sum ./
+COPY go.mod go.sum package.json yarn.lock ./
 RUN script/bootstrap
 
 COPY . .

README.md

@@ -452,14 +452,18 @@ and may be invoked directly. The provided entrypoints are:
 
 -   `script/bootstrap` — install everything needed to build and
     develop this repository, idempotently, assuming nothing is
-    present. `git`, `make`, and `go` come from the first of nix, apt,
-    brew, or apk found on the host, and are presence-checked only.
-    `golangci-lint` is deliberately **not** installed: it runs from a
-    digest-pinned image via `script/lint` and never from a host
-    install, so there is no host copy to drift from the pin. A missing
-    `docker` is warned about rather than installed or treated as
-    fatal — everything except linting works without it. Ends with
-    `go mod download`.
+    present. `git`, `make`, `go`, and `node` come from the first of nix,
+    apt, brew, or apk found on the host, and are presence-checked only;
+    `node` is an unpinned host runtime like the rest, because nvm's
+    prebuilt node is glibc-linked and does not run on this repo's
+    musl/Alpine build image. The Markdown formatter itself — `prettier` —
+    is pinned by `yarn.lock`'s integrity hash and installed with
+    `yarn install --frozen-lockfile`. `golangci-lint` is deliberately
+    **not** installed: it runs from a digest-pinned image via
+    `script/lint` and never from a host install, so there is no host copy
+    to drift from the pin. A missing `docker` is warned about rather than
+    installed or treated as fatal — everything except linting works
+    without it. Ends with `go mod download` and the `yarn` install.
 -   `script/setup` — make a fresh clone ready for development: runs
     `script/bootstrap`, then `script/install-precommit`.
 -   `script/projectname` — print this project's name (`sfdupes`).
@@ -490,10 +494,15 @@ and may be invoked directly. The provided entrypoints are:
     `go.sum` changes and the download layer goes cold again. Because
     the daemon only ever sees a build context, this works when the
     docker daemon is remote and bind mounts are impossible.
--   `script/fmt` — format the Go sources in place (`gofmt -s -w`).
-    Markdown is not formatted.
--   `script/fmt-check` — the read-only counterpart of `script/fmt`:
-    prints any unformatted file and exits non-zero instead of writing.
+-   `script/fmt` — format in place: `gofmt -s -w` for Go sources and
+    `prettier` for Markdown (`--tab-width 4 --prose-wrap always`, the
+    house settings, also carried in `.prettierrc`). prettier is the
+    pinned devDependency in `package.json`/`yarn.lock`, installed by
+    `script/bootstrap`.
+-   `script/fmt-check` — the read-only counterpart of `script/fmt`: runs
+    both checks, reports each independently so it is clear which failed,
+    and exits non-zero if either found unformatted files instead of
+    writing.
 -   `script/check` — run `script/test`, `script/lint`, and
     `script/fmt-check`, in that order. Modifies nothing. Needs
     `docker`, because `script/lint` does.
@@ -557,8 +566,8 @@ carries the compile recipe:
     `-v` on failure).
 -   `make lint` — run `golangci-lint` with the repo config, in Docker
     (see `script/lint`); requires `docker`.
--   `make fmt` / `make fmt-check` — format Go sources / verify
-    formatting without writing.
+-   `make fmt` / `make fmt-check` — format Go and Markdown sources /
+    verify both without writing.
 -   `make check` — `test`, `lint`, and `fmt-check`; modifies nothing.
     Requires `docker`, via `lint`.
 -   `make docker` — build the Docker image, which runs the gates as

TODO.md

@@ -29,6 +29,9 @@
 
 # Completed Steps
 
+- restore Markdown formatting in `script/fmt`/`fmt-check` and reformat
+  all Markdown to the house prettier settings (2026-09-21, closes
+  https://git.eeqj.de/sneak/sfdupes/issues/19)
 - fix the lint-image pin comments and `FROM` form in `Dockerfile` and
   `Dockerfile.lint` (2026-08-10, branch `next`, closes
   https://git.eeqj.de/sneak/sfdupes/issues/25): dropped the false

package.json

@@ -0,0 +1,5 @@
+{
+  "devDependencies": {
+    "prettier": "3.8.1"
+  }
+}

script/bootstrap

@@ -11,6 +11,12 @@ set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
+# yarn provides prettier, which formats Markdown. yarn is a tool, like
+# node/git/make/go below; the reference that governs formatting output is
+# prettier, pinned by yarn.lock's integrity hash and installed by
+# `yarn install --frozen-lockfile`.
+YARN_VERSION="1.22.22"
+
 PKGMGR=""
 SUDO=""
 APT_UPDATED=""
@@ -58,6 +64,21 @@ missing() {
     ! command -v "$1" >/dev/null 2>&1
 }
 
+ensure_node() {
+    if ! missing node; then return 0; fi
+    pkg_install nodejs nodejs node nodejs
+}
+
+ensure_yarn() {
+    if ! missing yarn; then return 0; fi
+    if ! missing corepack; then
+        corepack enable >/dev/null 2>&1 || true
+        corepack prepare "yarn@$YARN_VERSION" --activate
+    else
+        pkg_install yarn yarn yarn yarn
+    fi
+}
+
 main() {
     cd "$ROOT"
 
@@ -71,6 +92,16 @@ main() {
     if missing make; then pkg_install gnumake make make make; fi
     if missing go; then pkg_install go golang go go; fi
 
+    # node runs prettier and is an unpinned host tool for the same reason
+    # git/make/go are: it comes from the host package manager, whatever
+    # version it ships. It is not installed via nvm the way the canonical
+    # template does, because nvm's prebuilt node is glibc-linked and does
+    # not run on this repo's musl/Alpine build image. prettier — the tool
+    # whose version affects formatting output — is pinned by yarn.lock.
+    ensure_node
+    ensure_yarn
+    yarn install --frozen-lockfile
+
     # Linting runs via docker only (script/lint), so docker is a lint
     # prerequisite rather than something bootstrap installs. Warn, do
     # not fail: everything except `make lint` — and, through it,

script/fmt

@@ -1,12 +1,23 @@
 #!/bin/sh
-# script/fmt: format all files (writes).
+# script/fmt: format all files (writes). gofmt for Go, prettier for
+# Markdown. prettier is the pinned devDependency in package.json/
+# yarn.lock; script/bootstrap installs it (see run_prettier).
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
+run_prettier() {
+    if ! command -v yarn >/dev/null 2>&1; then
+        echo "fmt: yarn not found; run script/bootstrap first" >&2
+        exit 1
+    fi
+    yarn run prettier "$@"
+}
+
 main() {
     cd "$ROOT"
     gofmt -s -w .
+    run_prettier --write '**/*.md' --tab-width 4 --prose-wrap always
 }
 
 main "$@"

script/fmt-check

@@ -1,18 +1,37 @@
 #!/bin/sh
 # script/fmt-check: check formatting (read-only). Same scope as
-# script/fmt, but fails instead of writing.
+# script/fmt: gofmt for Go, prettier for Markdown. Both run every time
+# and each reports independently, so a failure names which formatter is
+# unhappy; the script exits non-zero if either found unformatted files.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
+run_prettier() {
+    if ! command -v yarn >/dev/null 2>&1; then
+        echo "fmt-check: yarn not found; run script/bootstrap first" >&2
+        exit 1
+    fi
+    yarn run prettier "$@"
+}
+
 main() {
     cd "$ROOT"
+    rc=0
+
     files="$(gofmt -s -l .)"
     if [ -n "$files" ]; then
         echo "gofmt: files not formatted:" >&2
         echo "$files" >&2
-        exit 1
+        rc=1
     fi
+
+    if ! run_prettier --check '**/*.md' --tab-width 4 --prose-wrap always; then
+        echo "prettier: Markdown not formatted; run make fmt" >&2
+        rc=1
+    fi
+
+    exit "$rc"
 }
 
 main "$@"

yarn.lock

@@ -0,0 +1,8 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+prettier@3.8.1:
+  version "3.8.1"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-3.8.1.tgz#edf48977cf991558f4fcbd8a3ba6015ba2a3a173"
+  integrity sha512-UOnG6LftzbdaHZcKoPFtOcCKztrQ57WkHDeRD9t/PTQtmT0NHSeWWepj6pS0z/N7+08BHFDQVUrfmfMRcZwbMg==