git pre-commit hook for format fix (#1730) - ux only

.githooks/pre-commit

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+# Run formatter from repository root regardless of current directory.
+REPO_ROOT="$(git rev-parse --show-toplevel)"
+cd "${REPO_ROOT}"
+
+# Capture the files already staged for commit so we only re-stage those
+# paths after formatting.
+staged_files=()
+while IFS= read -r -d '' file; do
+  staged_files+=("${file}")
+done < <(git diff --cached --name-only -z --diff-filter=ACMR)
+
+# Intentionally format all currently modified tracked C/C++ files.
+# The helper handles no-op cases and exits 0 when nothing matches.
+echo "Running clang-format fix before commit..."
+./bin/clang-format-fix
+
+# Ensure formatting changes are included in the pending commit without
+# staging unrelated tracked modifications from other files in the
+# working tree.
+if ((${#staged_files[@]})); then
+  git add -- "${staged_files[@]}"
+fi

bin/clang-format-fix

@@ -14,6 +14,7 @@ fi
 set -euo pipefail
 
 GIT_LS_FILES_FLAGS=""
+# -g scopes formatting to tracked files currently modified in git status.
 if [[ "${1:-}" == "-g" ]]; then
   GIT_LS_FILES_FLAGS="--modified"
 fi
@@ -21,6 +22,7 @@ fi
 CLANG_FORMAT_VERSION_RAW="$(${CLANG_FORMAT_BIN} --version)"
 CLANG_FORMAT_MAJOR="$(printf '%s\n' "${CLANG_FORMAT_VERSION_RAW}" | grep -oE '[0-9]+' | head -n1)"
 
+# Guard against local binaries older than the repo formatting config.
 if [[ -z "${CLANG_FORMAT_MAJOR}" || "${CLANG_FORMAT_MAJOR}" -lt 21 ]]; then
   echo "Error: ${CLANG_FORMAT_BIN} is too old: ${CLANG_FORMAT_VERSION_RAW}"
   echo "This repository's .clang-format requires clang-format 21 or newer."
@@ -37,9 +39,14 @@ fi
 # --exclude-standard: ignores files in .gitignore
 # Additionally exclude files in 'lib/EpdFont/builtinFonts/' as they are script-generated.
 # Also exclude files in 'lib/Epub/Epub/hyphenation/generated/' as they are script-generated.
+# Keep the no-match case non-fatal: grep returns 1 when no files match,
+# which is expected when there are no modified C/C++ files.
+set +o pipefail
 git ls-files  --exclude-standard ${GIT_LS_FILES_FLAGS} \
     | grep -E '\.(c|cpp|h|hpp)$' \
     | grep -v -E '^lib/EpdFont/builtinFonts/' \
     | grep -v -E '^lib/Epub/Epub/hyphenation/generated/' \
     | grep -v -E '^lib/uzlib/' \
     | xargs -r "${CLANG_FORMAT_BIN}" -style=file -i
+# Restore strict pipeline failure handling for the rest of the script.
+set -o pipefail

docs/contributing/development-workflow.md

@@ -6,6 +6,7 @@ This page defines the expected local workflow before opening a pull request.
 
 - Fork the repository to your own GitHub account
 - Clone your fork locally and add the upstream repository if needed
+- Enable repo hooks once per clone: `git config core.hooksPath .githooks && chmod +x .githooks/pre-commit`
 
 - Branch from `master`
 - Keep each PR focused on one fix or feature area

docs/contributing/getting-started.md

@@ -53,6 +53,13 @@ If you already cloned without submodules:
 git submodule update --init --recursive
 ```
 
+Enable the repository-managed Git hooks (required once per clone):
+
+```sh
+git config core.hooksPath .githooks
+chmod +x .githooks/pre-commit
+```
+
 ## Build
 
 ```sh