Fix --empty option of ifchange

Author: nobu

tool/ifchange

@@ -18,7 +18,7 @@ HELP
 set -e
 timestamp=
 keepsuffix=
-empty=
+srcavail=f
 color=auto
 until [ $# -eq 0 ]; do
     case "$1" in
@@ -39,7 +39,7 @@ until [ $# -eq 0 ]; do
 	    keepsuffix=`expr \( "$1" : '[^=]*=\(.*\)' \)`
 	    ;;
 	--empty)
-	    empty=yes
+	    srcavail=s
 	    ;;
 	--color)
 	    color=always
@@ -97,7 +97,7 @@ fi
 
 targetdir=
 case "$target" in */*) targetdir=`dirname "$target"`;; esac
-if [ -f "$target" -a ! -${empty:+f}${empty:-s} "$temp" ] || cmp "$target" "$temp" >/dev/null 2>&1; then
+if [ -f "$target" -a ! -${srcavail} "$temp" ] || cmp "$target" "$temp" >/dev/null 2>&1; then
     echo "$target ${msg_unchanged}unchanged${msg_reset}"
     rm -f "$temp"
 else

win32/ifchange.bat

@@ -62,7 +62,7 @@ set src=%src:/=\%
 
 if exist %dest% (
     if not exist %src% goto :nt_unchanged1
-    if "%empty%" == "" for %%I in (%src%) do if %%~zI == 0 goto :nt_unchanged
+    if not "%empty%" == "" for %%I in (%src%) do if %%~zI == 0 goto :nt_unchanged
     fc.exe %dest% %src% > nul && (
       :nt_unchanged
 	del %src%