diff --git a/.github/workflows/prek.yaml b/.github/workflows/prek.yaml
new file mode 100644
index 0000000..c936dc2
--- /dev/null
+++ b/.github/workflows/prek.yaml
@@ -0,0 +1,10 @@
+name: Prek checks
+"on": [push, pull_request]
+jobs:
+  prek:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - uses: j178/prek-action@v2
+        with:
+          extra-args: '-q'
diff --git a/.github/workflows/style.yml b/.github/workflows/style.yml
deleted file mode 100644
index 7211711..0000000
--- a/.github/workflows/style.yml
+++ /dev/null
@@ -1,22 +0,0 @@
-name: Check style
-on: [push, pull_request]  # yamllint disable-line rule:truthy
-jobs:
-  style:
-    defaults:
-      run:
-        shell: bash -l {0}
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v7
-        with:
-          fetch-depth: 1
-          show-progress: false
-      - run: sudo apt update
-      - name: Install shellcheck, checkbashisms, and yamllint
-        run: sudo apt -y install devscripts shellcheck shfmt yamllint
-      - name: Install markdownlint
-        run: npm install markdownlint-cli2 --global
-      - name: Install uv
-        uses: astral-sh/setup-uv@v9.0.0
-      - name: Check style
-        run: make style-check
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index d114f5e..3ffe2df 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1,5 +1,5 @@
 name: Run Small test
-on: [push, pull_request]  # yamllint disable-line rule:truthy
+on: [push, pull_request] # yamllint disable-line rule:truthy
 jobs:
   test:
     runs-on: ubuntu-latest
diff --git a/.ruff.toml b/.ruff.toml
new file mode 100644
index 0000000..501e1cd
--- /dev/null
+++ b/.ruff.toml
@@ -0,0 +1,69 @@
+line-length = 100
+output-format = "concise"
+
+[lint]
+preview = true
+extend-select = [
+  "I",
+  "D",
+  "DOC",
+  "B",
+  "A",
+  "COM",
+  "C4",
+  "DTZ",
+  "EM",
+  "EXE",
+  "FA",
+  "INT",
+  "ISC",
+  "ICN",
+  "PIE",
+  "PYI",
+  "Q",
+  "RET",
+  "SLF",
+  "SIM",
+  "SLOT",
+  "TID",
+  "TC",
+  "ARG",
+  "PTH",
+  "FLY",
+  "NPY",
+  "PD",
+  "N",
+  "PERF",
+  "E",
+  "W",
+  "F",
+  "PLC",
+  "PLE",
+  "UP",
+  "FURB",
+  "RUF",
+  "TRY",
+]
+extend-ignore = [
+  "COM812",
+  "D203",
+  "D213",
+  "D400",
+  "D413",
+  "DOC501",
+  "E266",
+  "EM101",
+  "PLC1901",
+  "RET504",
+  "SIM102",
+  "SIM108",
+  "TRY002",
+  "TRY003",
+  "TRY300",
+]
+
+[lint.pycodestyle]
+max-line-length = 100
+
+[format]
+docstring-code-format = false
diff --git a/.yamlfmt.yaml b/.yamlfmt.yaml
new file mode 100644
index 0000000..ef4ff50
--- /dev/null
+++ b/.yamlfmt.yaml
@@ -0,0 +1,4 @@
+formatter:
+  retain_line_breaks: true
+  scan_folded_as_literal: true
+  drop_unnecessary_doc_start: false
diff --git a/.yamllint.yaml b/.yamllint.yaml
new file mode 100644
index 0000000..38c68ba
--- /dev/null
+++ b/.yamllint.yaml
@@ -0,0 +1,5 @@
+extends: default
+
+rules:
+  document-start: disable
+  line-length: disable
diff --git a/Makefile b/Makefile
index 1d47c87..71701cd 100644
--- a/Makefile
+++ b/Makefile
@@ -7,11 +7,3 @@ test:
 
 clean:
 	${MAKE} -C tests clean
-
-PLUME_SCRIPTS ?= .plume-scripts
-
-# Code style; defines `style-check` and `style-fix`.
-ifeq (,$(wildcard ${PLUME_SCRIPTS}))
-dummy := $(shell git clone --depth=1 -q https://github.com/plume-lib/plume-scripts.git ${PLUME_SCRIPTS})
-endif
-include ${PLUME_SCRIPTS}/code-style.mak
diff --git a/prek.toml b/prek.toml
new file mode 100644
index 0000000..e935abf
--- /dev/null
+++ b/prek.toml
@@ -0,0 +1,234 @@
+# Configuration file for `prek`, a git hook framework written in Rust.
+# See https://prek.j178.dev for more information.
+#:schema https://www.schemastore.org/prek.json
+
+[[repos]]
+repo = "builtin"
+hooks = [
+  { id = "check-added-large-files" },
+  { id = "check-case-conflict" },
+  { id = "check-executables-have-shebangs", exclude = { glob = [
+    "search",
+  ] } },
+  { id = "check-json" },
+  { id = "check-merge-conflict" },
+  { id = "check-shebang-scripts-are-executable" },
+  { id = "check-symlinks", exclude = { glob = [
+    ".subversion/auth",
+    "dots/.subversion/auth",
+  ] } },
+  { id = "check-toml" },
+  { id = "check-vcs-permalinks" },
+  { id = "check-xml" },
+  { id = "check-yaml" },
+  { id = "destroyed-symlinks" },
+  { id = "detect-private-key" },
+  { id = "end-of-file-fixer", exclude = { glob = [
+    "bugs/jikes-patches/*",
+    "**/non-conflicted-file-without-terminator.txt",
+    "**/native-image/**",
+    "**/tests/squeeze-blank-lines-test/**",
+  ] } },
+  { id = "fix-byte-order-marker" },
+  { id = "forbid-new-submodules" },
+  { id = "mixed-line-ending" },
+  { id = "trailing-whitespace", exclude = { glob = [
+    "**/*.diff",
+    "**/*.diff3",
+    "**/*.patch",
+    "**/tests/squeeze-blank-lines-test/**",
+    ".aspell.en.prepl",
+    ".aspell.en.pws",
+    "bugs/BUGS.to-do",
+    "bugs/bug-mew",
+    "bugs/jikes-patches/*",
+    "dots/.aspell.en.prepl",
+    "dots/.aspell.en.pws",
+    "dots/en_US_apostrophe.aff",
+    "dots/enscript.st",
+    "emacs/bug/crypted.UUE",
+    "en_US_apostrophe.aff",
+    "enscript.st",
+  ] } },
+]
+
+## GitHub Actions
+
+[[repos]]
+repo = "https://github.com/rhysd/actionlint"
+rev = "v1.7.12"
+hooks = [{ id = "actionlint" }]
+
+## HTML
+
+[[repos]]
+repo = "https://github.com/Lucas-C/pre-commit-hooks-java"
+rev = "1.3.10"
+hooks = [{ id = "validate-html", exclude = { glob = ["**/bytopic-headfoot.html"] }}]
+
+## Makefiles
+
+[[repos]]
+repo = "https://github.com/checkmake/checkmake.git"
+rev = "0.2.2"
+hooks = [{ id = "checkmake" }]
+
+## Markdown
+
+[[repos]]
+repo = "https://github.com/DavidAnson/markdownlint-cli2"
+rev = "v0.23.1"
+hooks = [{ id = "markdownlint-cli2" }]
+
+## Pre-commit itself
+
+[[repos]]
+repo = "https://github.com/pre-commit/sync-pre-commit-deps"
+rev = "v0.0.4"
+hooks = [{ id = "sync-pre-commit-deps" }]
+
+## Python
+
+[[repos]]
+repo = "https://github.com/astral-sh/ruff-pre-commit"
+rev = "v0.15.22" # Ruff version.
+hooks = [
+  # Run the linter.
+  { id = "ruff-check", args = ["--fix"], types_or = ["python", "pyi"] },
+
+  # Run the formatter.
+  { id = "ruff-format", types_or = ["python", "pyi"] },
+]
+
+[[repos]]
+repo = "https://github.com/astral-sh/ty-pre-commit"
+rev = "v0.0.62"                                       # ty version.
+hooks = [{ id = "ty", types_or = ["python", "pyi"] }]
+
+[[repos]]
+repo = "https://github.com/asottile/pyupgrade"
+rev = "v3.21.2"
+hooks = [{ id = "pyupgrade" }]
+
+## Secrets
+
+[[repos]]
+repo = "https://github.com/gitleaks/gitleaks"
+rev = "v8.24.2"
+hooks = [{ id = "gitleaks", exclude = { glob = ["**/AdjacentTest*"] } }]
+
+[[repos]]
+repo = "https://github.com/Yelp/detect-secrets"
+rev = "v1.5.0"
+hooks = [{ id = "detect-secrets", exclude = { glob = ["**/AdjacentTest*"] } }]
+
+## Shell scripts
+
+[[repos]]
+repo = "https://github.com/shellcheck-py/shellcheck-py"
+rev = "v0.11.0.1"
+hooks = [
+  { id = "shellcheck", args = [
+    "-x",
+    "-P",
+    "SCRIPTDIR",
+  ], exclude = { glob = [
+    "share/csail-athena-tickets.bash",
+    "share/addrfilter",
+    "share/print-mail",
+    "share/javapp",
+    "share/myxapps",
+    "cronic-orig",
+    "classfile_check_version",
+  ] } },
+]
+
+[[repos]]
+repo = "https://github.com/scop/pre-commit-shfmt"
+rev = "v3.13.1-1"
+hooks = [
+  { id = "shfmt", args = [
+    "-i",
+    "2",
+    "-ci",
+    "-bn",
+    "-sr",
+  ], exclude = { glob = [
+    "gradlew",
+    "share/addrfilter",
+    "dots/conda-initialize.sh",
+    "conda-initialize.sh",
+  ] } },
+]
+
+# TODO: checkbashisms (I need to write my own).
+# [[repos]]
+# repo = "TODO"
+# hooks = [
+#   { id = "checkbashisms", types = [
+#     "shell",
+#   ], exclude = { glob = [
+#     "share/addrfilter",
+#     "share/print-mail",
+#     "share/myxapps",
+#     "share/javapp",
+#     "gradlew",
+#   ] } },
+# ]
+
+# Problems:
+# * False positives for E011.
+# * It requires indent to be a multiple of 4.
+# [[repos]]
+# repo = "https://github.com/openstack/bashate"
+# rev = "2.1.1"
+# hooks = [
+#     { id = "bashate", exclude = { glob = ["share/csail-athena-tickets.bash" ] } },
+# ]
+
+## Text
+
+# Very noisy.
+# [[repos]]
+# repo = "https://github.com/errata-ai/vale"
+# rev = "16d3a7f"
+# hooks = [ #{id = "vale", name = "vale sync",         pass_filenames = false,         args =  ["sync"], },
+#   { id = "vale", args = [
+#     "--output=line",
+#     "--minAlertLevel=error",
+#   ] },
+# ]
+
+# Very disruptive.  Perhaps re-enable later.
+# [[repos]]
+# repo = "https://github.com/crate-ci/typos"
+# rev = "v1.48.0"
+# hooks = [
+#     { id = "typos", exclude = { glob = [".abbrev_defs", "share/mail-review-spam", "bugs/jikes-patches/*", "share/checkbashisms", "dots/.aspell.en.prepl", ".aspell.en.prepl", "dots/en_US_apostrophe.dic", "dots/.aspell.en.pws", ".aspell.en.pws", "dots/en_US_apostrophe.aff", "en_US_apostrophe.aff" ] } }
+# ]
+
+# Very noisy.  Perhaps re-enable later.
+# [[repos]]
+# repo = "https://github.com/codespell-project/codespell"
+# rev = "v2.4.1"
+# hooks = [
+#     { id = "codespell", exclude = { glob = [ "en_US_apostrophe.dic", ".ssh/known_hosts", "enscript.st" ] } },
+# ]
+
+# proselint does not understand fenced code blocks in markdown files.
+# [[repos]]
+# repo = "https://github.com/amperser/proselint"
+# rev = "v0.16.0"
+# hooks = [{ id = "proselint", args = ["check"],  }]
+
+## YAML
+
+[[repos]]
+repo = "https://github.com/google/yamlfmt"
+rev = "v0.19.0"
+hooks = [{ id = "yamlfmt" }]
+
+[[repos]]
+repo = "https://github.com/adrienverge/yamllint.git"
+rev = "v1.29.0"
+hooks = [{ id = "yamllint" }]
diff --git a/tests/Makefile b/tests/Makefile
index 375b00a..c6052c2 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -1,3 +1,5 @@
+.PHONY: all clean test
+
 test:
 	${MAKE} -C git-clone-related-test test
 	${MAKE} -C resolve-adjacent-conflicts-test
diff --git a/tests/git-clone-related-test/Makefile b/tests/git-clone-related-test/Makefile
index a476804..f3187c0 100644
--- a/tests/git-clone-related-test/Makefile
+++ b/tests/git-clone-related-test/Makefile
@@ -1,7 +1,9 @@
+.PHONY: all clean test
+
 test: test1 test2 test3 test4 test5 test6 test7 test8 test9 test10
 
 # Here are the repositories and branches that exist.
-# 
+#
 # Upstreams:
 # plume-lib/git-clone-related-test-repo1
 #  * branch-upstream-all
@@ -14,7 +16,7 @@ test: test1 test2 test3 test4 test5 test6 test7 test8 test9 test10
 #  * branch-fallback
 # plume-lib/git-clone-related-test-repo3
 #  * branch-fallback
-# 
+#
 # Forks:
 # mernst/git-clone-related-test-repo1
 #  * branch-downstream-all
@@ -25,7 +27,7 @@ test: test1 test2 test3 test4 test5 test6 test7 test8 test9 test10
 #  * branch-downstream-all
 #  * branch-fallback
 # DOES NOT EXIST: mernst/git-clone-related-test-repo3
-# 
+#
 # The tests run commands from clones of the two repo1 repositories,
 # trying to create clones of the repo2 and repo3 repositories.
 
@@ -33,17 +35,17 @@ test: test1 test2 test3 test4 test5 test6 test7 test8 test9 test10
 #  * branch ${MYBRANCH} of https://github.com/${MYORG}/${REPO_NAME}.git
 #    test1: mernst/repo1, branch-downstream-all => mernst/repo2, branch-downstream-all
 #    test2: plume-lib/repo1, branch-upstream-all => plume-lib/repo2, branch-upstream-all
-# 
+#
 #  * branch ${MYBRANCH} of https://github.com/${UPSTREAM_ORG}/${REPO_NAME}.git
 #    test3: mernst/repo1, branch-not-in-downstream-repo2 => plume-lib/repo2, branch-not-in-downstream-repo2
 #    test4: plume-lib/repo1, branch-not-in-downstream-repo2 => plume-lib/repo2, branch-not-in-downstream-repo2
 #    test9: mernst/repo1, master => plume-lib/repo3, master
 #    test10: mernst/repo1, branch-fallback => plume-lib/repo3, branch-fallback
-# 
+#
 #  * branch ${FALLBACK_BRANCH} of https://github.com/${UPSTREAM_ORG}/${REPO_NAME}.git
 #    test5: mernst/repo1, branch-downstream-repo1 => plume-lib/repo2, master
 #    test6: plume-lib/repo1, branch-upstream-repo1 => plume-lib/repo2, master
-# 
+#
 #  * branch ${FALLBACK_BRANCH} of https://github.com/${UPSTREAM_ORG}/${REPO_NAME}.git
 #    test7: mernst/repo1, branch-downstream-repo1 => plume-lib/repo2, branch-fallback
 #    test8: plume-lib/repo1, branch-upstream-repo1 => plume-lib/repo2, branch-fallback
@@ -90,5 +92,5 @@ test10:
 	USER=mernst ./test-git-clone-related.sh https://github.com/mernst/git-clone-related-test-repo1 branch-fallback "plume-lib git-clone-related-test-repo3" https://github.com/plume-lib/git-clone-related-test-repo3.git branch-fallback
 
 
-clean: 
+clean:
 # Nothing to do
diff --git a/tests/resolve-adjacent-conflicts-test/Makefile b/tests/resolve-adjacent-conflicts-test/Makefile
index 0a642cc..4891241 100644
--- a/tests/resolve-adjacent-conflicts-test/Makefile
+++ b/tests/resolve-adjacent-conflicts-test/Makefile
@@ -1,5 +1,8 @@
+.PHONY: all clean test
+
 RESOLVER=../../resolve-adjacent-conflicts
 
+.PHONY: diff
 test: diff
 
 diff: Merged_ConflictStyleMerge.diff Merged_ConflictStyleDiff3.diff
diff --git a/tests/resolve-import-conflicts-test/Makefile b/tests/resolve-import-conflicts-test/Makefile
index 7147848..fc01adf 100644
--- a/tests/resolve-import-conflicts-test/Makefile
+++ b/tests/resolve-import-conflicts-test/Makefile
@@ -1,7 +1,10 @@
+.PHONY: all clean test
+
 RESOLVER=../../resolve-import-conflicts
 
 test: diff
 
+.PHONY: diff
 diff: Merged_ConflictStyleMerge.diff Merged_ConflictStyleDiff3.diff
 
 Merged_ConflictStyleMerge.diff: Merged_ConflictStyleMerge.goal Merged_ConflictStyleMerge.java