[PATCH v2 0/4] making test-suite tracing more useful

This series fixes some rough edges in the "-x" feature of the test suite. With it, it should be possible to turn on tracing for CI runs.

This is mostly a repost of v1 at:

  https://public-inbox.org/git/20171019210140.64lb52cqtgdh22ew@sigill.intra.peff.net

which had some discussion, but wasn't picked up.

I fixed a few typos pointed out by reviewers, and I tried to summarize the discussion around "magic descriptor 4" in the commit message of patch 2. My conclusion there was that none of the options is particularly good. The only thing thing that might make sense is making "7" the magical descriptor. But given that "4" only had one troubling call, I'm inclined to just leave it as-is and see if this ever comes up again (especially if we start using "-x" in the Travis builds, then we'd catch any problems).

  [1/4]: test-lib: silence "-x" cleanup under bash
  [2/4]: t5615: avoid re-using descriptor 4
  [3/4]: test-lib: make "-x" work with "--verbose-log"
  [4/4]: t/Makefile: introduce TEST_SHELL_PATH

 Makefile                 |  8 ++++++++
 t/Makefile               |  6 ++++--
 t/t5615-alternate-env.sh |  6 +++---
 t/test-lib.sh            | 46 +++++++++++++++++++++++++++++++++-------------
 4 files changed, 48 insertions(+), 18 deletions(-)

-Peff