gnulib-tool: better error handling

[Bruno Haible]

This makes for a better error handling during "patch".

2006-08-26  Bruno Haible  <address@hidden>

        * gnulib-tool (func_verify_module): Check against misapplying patch.

*** gnulib-20060823/gnulib-tool 2006-08-24 03:52:14.000000000 +0200
--- gnulib-20060823-modified/gnulib-tool        2006-08-26 23:21:27.000000000 
+0200
***************
*** 639,645 ****
       && test "TEMPLATE" != "$module" \
       && test "TEMPLATE-TESTS" != "$module"; then
      # OK, $module is a correct module name.
!     :
    else
      echo "gnulib-tool: module $module doesn't exist" 1>&2
      module=
--- 639,646 ----
       && test "TEMPLATE" != "$module" \
       && test "TEMPLATE-TESTS" != "$module"; then
      # OK, $module is a correct module name.
!     # Verify that building the module description with 'patch' succeeds.
!     func_lookup_file "modules/$module"
    else
      echo "gnulib-tool: module $module doesn't exist" 1>&2
      module=