[PATCH v3 7/7] t/README: Add a note about the dangers of coverage chasing

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Having no coverage at all is almost always a bad sign, but trying to
attain 100% coverage everywhere is usually a waste of time. Add a
paragraph to explain this to future test writers.

Inspired-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---

Jonathan doesn't particularly like this one. I have no particular
preference, just trying to get across the point that you shouldn't
cargo-cult-coverage.

 t/README |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/t/README b/t/README
index 15d4b52..4fe8d50 100644
--- a/t/README
+++ b/t/README
@@ -271,6 +271,15 @@ Do:
  - Check the test coverage for your tests. See the "Test coverage"
    below.
 
+   Don't blindly follow test coverage metrics, they're a good way to
+   spot if you've missed something. If a new function you added
+   doesn't have any coverage you're probably doing something wrong,
+   but having 100% coverage doesn't necessarily mean that you tested
+   everything.
+
+   Tests that are likely to smoke out future regressions are better
+   than tests that just inflate the coverage metrics.
+
 Don't:
 
  - exit() within a <script> part.
-- 
1.7.0.4