cmake: Followup on release commit automation.

This is a followup on 93f906e2.

Simplify the FileIterator interface by doing the eof check in
fi_get_next_line().

Add rollback instructions to final instructions message.

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

cmake/FileIterator.cmake

@@ -2,7 +2,9 @@
 
 function(fi_open_file file)
     file(READ "${file}" fi_file_contents)
+
     set(fi_file_contents "${fi_file_contents}" PARENT_SCOPE)
+    set(fi_done          FALSE                 PARENT_SCOPE)
 endfunction()
 
 function(fi_get_next_line)
@@ -14,11 +16,6 @@ function(fi_get_next_line)
 
     string(SUBSTRING "${fi_file_contents}" ${pos} -1 fi_file_contents)
 
-    set(fi_line          "${fi_line}"          PARENT_SCOPE)
-    set(fi_file_contents "${fi_file_contents}" PARENT_SCOPE)
-endfunction()
-
-function(fi_check_done)
     string(LENGTH "${fi_file_contents}" len)
 
     set(fi_done FALSE PARENT_SCOPE)
@@ -26,4 +23,7 @@ function(fi_check_done)
     if(len EQUAL 0)
         set(fi_done TRUE PARENT_SCOPE)
     endif()
+
+    set(fi_line          "${fi_line}"          PARENT_SCOPE)
+    set(fi_file_contents "${fi_file_contents}" PARENT_SCOPE)
 endfunction()

cmake/MakeReleaseCommitAndTag.cmake

@@ -182,8 +182,6 @@ Ignore the following cmake error.
         endif()
 
         file(APPEND ${work_file} "${fi_line}" "\n")
-
-        fi_check_done()
     endwhile()
 
     # Convert to UNIX line endings on Windows, just copy the file otherwise.
@@ -242,6 +240,12 @@ Run the following commands to push the release commit and tag:
     git push
     git push --tags
 
+**** TO UNDO THE RELEASE ****
+
+To rollback these changes, run this command:
+
+    cmake .. -DTAG_RELEASE=UNDO
+
 Ignore the "configuration incomplete" message following, this mode does not
 build anything.