[PATCH 0/3] "-x" tracing option for tests

These patches are pulled out of the prune-mtime series I posted earlier[1]. The discussion veered off and there's no reason that the two topics need to be part of the same series.

The first patch is the same cleanup as before.

The second one uses Michael's suggested "verbose" function, like:

  $ verbose test 1 = 2
  command failed: 'test' '1' '=' '2'

(you can see that I used rev-parse's --sq-quote, which is a little eager to use quotes where they are not needed. I wonder if we should teach it to produce prettier output when there is nothing outside of [A-Za-z0-9=] or similar).

The third one is a cleanup of the "set -x" patch I posted earlier. I made the implementation a little less gross, the output a little cleaner, and wired it up to "-x". I think it's clean enough and useful enough to add to our bag of test-debugging tricks.

  [1/3]: t5304: use test_path_is_* instead of "test -f"
  [2/3]: t5304: use helper to report failure of "test foo = bar"
  [3/3]: test-lib.sh: support -x option for shell-tracing

-Peff

[1] http://thread.gmane.org/gmane.comp.version-control.git/257850/focus=257859