ifchange: no overwrite with an empty file

* tool/ifchange, win32/ifchange.bat: do not overwrite with an empty
  file by default, and add --empty option to force it.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43519 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 16 insertions, 4 deletions

diff --git a/tool/ifchange b/tool/ifchange
index 5695e5a9b8..488e9db26e 100755
--- a/tool/ifchange
+++ b/tool/ifchange
@@ -4,6 +4,7 @@
 set -e
 timestamp=
 keepsuffix=
+empty=
 until [ $# -eq 0 ]; do
     case "$1" in
 	--timestamp)
@@ -18,6 +19,9 @@ until [ $# -eq 0 ]; do
 	--keep=*)
 	    keepsuffix=`expr \( "$1" : '[^=]*=\(.*\)' \)`
 	    ;;
+	--empty)
+	    empty=yes
+	    ;;
 	*)
 	    break
 	    ;;
@@ -33,7 +37,7 @@ if [ "$temp" = - ]; then
     trap 'rm -f "$temp"' 0
 fi
 
-if cmp "$target" "$temp" >/dev/null 2>&1; then
+if [ -f "$target" -a ! -${empty:+f}${empty:-s} "$temp" ] || cmp "$target" "$temp" >/dev/null 2>&1; then
     echo "$target unchanged"
     rm -f "$temp"
 else
diff --git a/win32/ifchange.bat b/win32/ifchange.bat
index 1444d1bc2f..ed10914953 100755
--- a/win32/ifchange.bat
+++ b/win32/ifchange.bat
@@ -3,6 +3,7 @@
 

 set timestamp=

 set keepsuffix=

+set empty=

 :optloop

 for %%I in (%1) do set opt=%%~I

 if "%opt%" == "--timestamp" (

@@ -21,6 +22,10 @@ if "%opt%" == "--timestamp" (
     set keepsuffix=%opt:~7%

     shift

     goto :optloop

+) else if "%opt%" == "--empty" (

+    set empty=yes

+    shift

+    goto :optloop

 )

 if "%opt%" == "" goto :end

 

@@ -66,15 +71,18 @@ del %2
 goto :end

 

 :nt

-if not exist %src% goto :end

 if exist %dest% (

+    if not exist %src% goto :nt_unchanged1

+    if "%empty%" == "" for %%I in (%src%) do if %%~zI == 0 goto :nt_unchanged

     fc.exe %dest% %src% > nul && (

-	echo %1 unchanged.

+      :nt_unchanged

 	del %src%

+      :nt_unchanged1

+	for %%I in (%1) do echo %%~I unchanged

 	goto :nt_end

     )

 )

-echo %1 updated.

+for %%I in (%1) do echo %%~I updated

 copy %src% %dest% > nul

 del %src%