hgview #3527 big commit takes ages to display [validation pending]

on big commit (mostly initial commit) or commits with binary files, hgview freezes.

Propose a heuristic where when there is more than say 10 files modified only the file names are shown with the possibility to show the diff.

Also need to make sure we don't display binaries.

appeared in<not specified>
done in1.0.0
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