feat(tools/shellfmt): accept positional file args for scoped format

When called without arguments, lib/tools/shellfmt.sh keeps its current
behaviour — aggregate every .sh/.conf/.inc/.csc/.tvb under compile.sh,
config/boards, config/sources, lib, and extensions and shfmt -w the
lot (CI-style mass-format).

When called with positional file arguments, only those files are
formatted, filtered against the same extension allowlist so a stray
.py / .md / .yml doesn't sneak through. .editorconfig still drives the
actual rules — shfmt picks it up regardless.

This lets editor-driven workflows (post-edit hooks, agent helpers)
scope the format to the file the user just touched without dragging
the whole tree into the next commit. Previously the wrapper silently
ignored file arguments and reformatted everything.

Verified:
  - bash lib/tools/shellfmt.sh                       → full-tree run as before
  - bash lib/tools/shellfmt.sh extensions/apa.sh     → only apa.sh formatted
  - bash lib/tools/shellfmt.sh foo.py extensions/apa.sh
                                                     → .py skipped (unsupported
                                                       extension), apa.sh
                                                       formatted.

Author: iav

lib/tools/shellfmt.sh

@@ -58,20 +58,64 @@ fi
 ACTUAL_VERSION="$("${SHELLFMT_BIN}" -version)"
 echo "Running shellfmt ${ACTUAL_VERSION}"
 
+# Resolve positional args to absolute paths BEFORE chdir, so callers
+# from sub-directories can pass relative paths and have them keep
+# meaning. Avoid `realpath -m` — its `-m` flag is GNU-only and breaks
+# on the macOS realpath(1) the script's darwin branch otherwise
+# supports. Plain `$PWD/path` prefix is enough; shfmt doesn't care
+# about symlink canonicalisation or `..` normalisation, and the
+# missing-file branch below still triggers on dangling paths.
+declare -a SCOPED_ARGS=()
+for _f in "$@"; do
+	if [[ "${_f}" == /* ]]; then
+		SCOPED_ARGS+=("${_f}")
+	else
+		SCOPED_ARGS+=("${PWD}/${_f}")
+	fi
+done
+
 cd "${SRC}"
 #"${SHELLFMT_BIN}" --help
 #"${SHELLFMT_BIN}" -f "${SRC}"
 #"${SHELLFMT_BIN}" -d "${SRC}"
 
 # Should match the .editorconfig
 
-# Aggregate all files that should be formatted
-board_config_files=$(find config/boards -type f \( -name "*.conf" -o -name "*.csc" -o -name "*.tvb" \))  # All board config files
-family_config_files=$(find config/sources -type f \( -name "*.conf" -o -name "*.inc" -o -name "*.sh" \)) # All family config files
-lib_files=$(find lib -type f -name "*.sh")                                                               # All build framework shell files
-extensions_files=$(find extensions -type f -name "*.sh")                                                 # All extension shell files
-
-declare -a ALL_BASH_FILES=(compile.sh ${board_config_files} ${family_config_files} ${lib_files} ${extensions_files})
+# Allowed file extensions for both full-tree and scoped modes; keep
+# in sync with the find globs below.
+ALLOWED_EXT_RE='\.(sh|conf|inc|csc|tvb)$'
+
+declare -a ALL_BASH_FILES=()
+
+if ((${#SCOPED_ARGS[@]} > 0)); then
+	# Scoped mode: only format the files passed on the command line.
+	# Skip anything that doesn't match the allowed extensions so a
+	# stray Python/Markdown/YAML argument doesn't sneak through.
+	echo -e "\nScoped mode: formatting only the files passed on argv"
+	for f in "${SCOPED_ARGS[@]}"; do
+		if [[ ! -e "${f}" ]]; then
+			echo "  skip (missing): ${f}"
+			continue
+		fi
+		if [[ ! "${f}" =~ ${ALLOWED_EXT_RE} ]]; then
+			echo "  skip (unsupported extension): ${f}"
+			continue
+		fi
+		ALL_BASH_FILES+=("${f}")
+	done
+	if ((${#ALL_BASH_FILES[@]} == 0)); then
+		echo "No eligible files after filtering — nothing to do."
+		exit 0
+	fi
+else
+	# Full-tree mode: aggregate every file the framework cares about.
+	board_config_files=$(find config/boards -type f \( -name "*.conf" -o -name "*.csc" -o -name "*.tvb" \))  # All board config files
+	family_config_files=$(find config/sources -type f \( -name "*.conf" -o -name "*.inc" -o -name "*.sh" \)) # All family config files
+	lib_files=$(find lib -type f -name "*.sh")                                                               # All build framework shell files
+	extensions_files=$(find extensions -type f -name "*.sh")                                                 # All extension shell files
+
+	ALL_BASH_FILES=(compile.sh ${board_config_files} ${family_config_files} ${lib_files} ${extensions_files})
+fi
 
 echo -e "\nAll files:" "${ALL_BASH_FILES[@]}"