Use template for jujutsu file listing

[joeri]

In jujutsu users can configure the default behaviour of jj file list so that it no longer puts out file names separated by newlines (which is the default behaviour). This means the output of jj file list can't be trusted to be stable. On the other hand the same mechanism allows you to output the files separated with a null byte without invoking tr, this has the additional benefit that filenames with newlines in them are now working.

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Thanks!

[bbatsov]

Thanks!