Hi all,

The default when creating a clock report is to use :scope file.  I find
it not practical for big files, where the report can take long to build.

I'm thinking of applying this change: when called from within a subtree,
`C-c C-x C-r' will insert a clock report with ":scope subtree", and use
":scope subtree" elsewhere.

Please let me know if you think that's a bad idea.