.editorconfig: add script to check and fix style issues

The various checks cover all settings in the `.editorconfig` file.
The `--fix` support, however, does not attempt to correct charset
issues because the encoding cannot be determined automatically.

Note that image files as well as generated files in the repository
are exempted from all style checks.

tools/Makefile.am

@@ -33,6 +33,7 @@ CLEANFILES = $(bin_SCRIPTS) $(dist_noinst_SCRIPTS)
 
 EXTRA_DIST = check-po.awk libtool-get-dll-ext mustek600iin-off.c \
 	     RenSaneDlls.cmd README xerox
+EXTRA_DIST += style-check.sh
 
 sane_find_scanner_SOURCES = sane-find-scanner.c
 if have_usblib

tools/style-check.sh

@@ -0,0 +1,96 @@
+#!/bin/sh -u
+# tools/style-check.sh -- for conformance or --fix to conform
+# Copyright (C) 2017  Olaf Meeuwissen
+#
+# License: GPL-3.0+
+
+check_final_newline() {
+    test x = "x$(tail -c 1 $1)"
+}
+
+insert_final_newline() {
+    check_final_newline $1 || echo >> $1
+}
+
+check_trailing_whitespace() {
+    test -z "$(sed -n '/[ \t]$/{p;q}' $1)"
+}
+
+trim_trailing_whitespace() {
+    sed -i 's/[ \t]*$//' $1
+}
+
+check_trailing_blank_lines() {
+    test -z "$(sed -n '${/^$/s/^/blank/p}' $1)"
+}
+
+trim_trailing_blank_lines() {
+    sed -i -e :a -e '/^\n*$/{$d;N;};/\n$/ba' $1
+}
+
+check_leading_blank_lines() {
+    test -z "$(sed -n '1{/^$/s/^/blank/p;q}' $1)"
+}
+
+trim_leading_blank_lines() {
+    sed -i '/./,$!d' $1
+}
+
+check_utf_8_charset() {
+    err=$(iconv -f utf-8 -t utf-8 < $1 2>&1 > /dev/null)
+    if test x != "x$err"; then
+        echo "charset not UTF-8: $1" >&2
+        echo "$err" >&2
+        return 1
+    fi
+}
+
+fix=false
+case $1 in
+    --fix) fix=true; shift;;
+esac
+
+status=0
+for file in "$@"; do
+    case $file in
+        COPYING) ;;                 # hands off of the GPL
+        *.gif) ;;                   # don't touch image files
+        *.jpg) ;;
+        *.png) ;;
+        *.pnm) ;;
+        Makefile.in) ;;             # skip automake outputs
+        */Makefile.in) ;;
+        aclocal.m4) ;;              # skip autoconf outputs
+        include/sane/config.h.in) ;;
+        m4/libtool.m4) ;;           # courtesy of libtool
+        m4/lt~obsolete.m4) ;;
+        ABOUT-NLS) ;;               # courtesy of gettext
+        doc/doxygen-*.conf.in) ;;   # don't fix doxygen -g comments
+
+        *)
+            if `$fix`; then
+                trim_trailing_whitespace $file
+                insert_final_newline $file
+                trim_trailing_blank_lines $file
+            else
+                if ! check_trailing_whitespace $file; then
+                    status=1
+                    echo "trailing whitespace: $file" >&2
+                fi
+                if ! check_final_newline $file; then
+                    status=1
+                    echo "final newline missing: $file" >&2
+                fi
+                if ! check_trailing_blank_lines $file; then
+                    status=1
+                    echo "trailing blank lines: $file" >&2
+                fi
+                if ! check_utf_8_charset $file; then
+                    status=1
+                fi
+            fi
+            ;;
+    esac
+done
+
+exit $status