check (non-)executable files -- and eliminate them manually from the repository)

--- a/Admin/Release/CHECKLIST	Sun Oct 21 18:32:33 2018 +0200
+++ b/Admin/Release/CHECKLIST	Sun Oct 21 19:34:11 2018 +0200
@@ -20,6 +20,10 @@
 - test Windows 10 subsystem for Linux:
   https://docs.microsoft.com/en-us/windows/wsl/install-win10
 
+- check (non-)executable files:
+    $ find . "(" -name "*.thy" -o -name "*.ML" -o -name "*.scala" -o -name ROOT ")" -executable
+    $ find -type f -executable
+
 - check sources:
     isabelle check_sources '~~' '$AFP_BASE'
     isabelle imports -M -a -d '~~/src/Benchmarks'

--- a/src/Pure/Admin/build_release.scala	Sun Oct 21 18:32:33 2018 +0200
+++ b/src/Pure/Admin/build_release.scala	Sun Oct 21 19:34:11 2018 +0200
@@ -227,10 +227,7 @@
 
           make_contrib(release.isabelle_dir)
 
-          execute(release.isabelle_dir,
-            """find . "(" -name "*.thy" -o -name "*.ML" -o -name "*.scala" ")" -print | xargs chmod -f -x""")
-          execute(release.isabelle_dir,
-            """find . -print | xargs chmod -f u+rw""")
+          execute(release.isabelle_dir, """find . -print | xargs chmod -f u+rw""")
 
 
           /* build tools and documentation */