docs: add documentation snippet for meson test console output changes

docs/markdown/snippets/meson_test_logs.md

@@ -0,0 +1,29 @@
+## New logging format for `meson test`
+
+The console output format for `meson test` has changed in several ways.
+The major changes are:
+
+* if stdout is a tty, `meson` includes a progress report.
+
+* if `--print-errorlogs` is specified, the logs are printed as test runs
+rather than afterwards.  All the error logs are printed rather than only
+the first ten.
+
+* if `--verbose` is specified and `--num-processes` specifies more than
+one concurrent test, test output is buffered and printed after the
+test finishes
+
+* the console logs include a reproducer command.  If `--verbose` is
+specified, the command is printed for all tests at the time they starts;
+otherwise, it is printed for failing tests at the time the test finishes
+
+* for TAP tests, Meson is able to report individual subtests.  If
+`--verbose` is specified, all tests are reported.  If `--print-errorlogs`
+is specified, only failures are.
+
+In addition, if `--verbose` was specified, Meson used not to generate
+logs.  This limitation has now been removed.
+
+These changes make the default `ninja test` output more readable, while
+`--verbose` output is provides detailed but human-readable logs that
+are well suited to CI environments.