t/README: Document the Smoke testing

Git now has a smoke testing service at http://smoke.git.nix.is that
anyone can send reports to. Change the t/README file to mention this.
Signed-off-by: NÆvar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/README

@@ -554,3 +554,69 @@ the purpose of t0000-basic.sh, which is to isolate that level of
 validation in one place.  Your test also ends up needing
 updating when such a change to the internal happens, so do _not_
 do it and leave the low level of validation to t0000-basic.sh.
+
+Smoke testing
+-------------
+
+The Git test suite has support for smoke testing. Smoke testing is
+when you submit the results of a test run to a central server for
+analysis and aggregation.
+
+Running a smoke tester is an easy and valuable way of contributing to
+Git development, particularly if you have access to an uncommon OS on
+obscure hardware.
+
+After building Git you can generate a smoke report like this in the
+"t" directory:
+
+    make clean smoke
+
+You can also pass arguments via the environment. This should make it
+faster:
+
+    GIT_TEST_OPTS='--root=/dev/shm' TEST_JOBS=10 make clean smoke
+
+The "smoke" target will run the Git test suite with Perl's
+"TAP::Harness" module, and package up the results in a .tar.gz archive
+with "TAP::Harness::Archive". The former is included with Perl v5.10.1
+or later, but you'll need to install the latter from the CPAN. See the
+"Test coverage" section above for how you might do that.
+
+Once the "smoke" target finishes you'll see a message like this:
+
+    TAP Archive created at <path to git>/t/test-results/git-smoke.tar.gz
+
+To upload the smoke report you need to have curl(1) installed, then
+do:
+
+    make smoke_report
+
+To upload the report anonymously. Hopefully that'll return something
+like "Reported #7 added.".
+
+If you're going to be uploading reports frequently please request a
+user account by E-Mailing gitsmoke@v.nix.is. Once you have a username
+and password you'll be able to do:
+
+    SMOKE_USERNAME=<username> SMOKE_PASSWORD=<password> make smoke_report
+
+Once the report is uploaded it'll be made available at
+http://smoke.git.nix.is, here's an overview of Recent Smoke Reports
+for Git:
+
+    http://smoke.git.nix.is/app/projects/smoke_reports/1
+
+The reports will also be mirrored to GitHub every few hours:
+
+    http://github.com/gitsmoke/smoke-reports
+
+The Smolder SQLite database is also mirrored and made available for
+download:
+
+    http://github.com/gitsmoke/smoke-database
+
+Note that the database includes hashed (with crypt()) user passwords
+and E-Mail addresses. Don't use a valuable password for the smoke
+service if you have an account, or an E-Mail address you don't want to
+be publicly known. The user accounts are just meant to be convenient
+labels, they're not meant to be secure.