tests: add test showing puzzling test output with (glob) lines

When using multiple (glob) lines, the test runner often moves the
lines around in the output on failure. I have run into this problem
many times. The added test shows one example of this. Note that it
doesn't show the mismatching lines and instead shows diff hunks that
appear to replace a literal by a glob, and other hunks that should
clearly match.

Differential Revision: https://phab.mercurial-scm.org/D3880

tests/test-run-tests.t

@@ -120,6 +120,52 b' test churn with globs'
   python hash seed: * (glob)
   [1]
 
+test how multiple globs gets matched with lines in output
+  $ cat > test-failure-globs.t <<EOF
+  >   $ echo "context"; echo "context"; \
+  >     echo "key: 1"; echo "value: not a"; \
+  >     echo "key: 2"; echo "value: not b"; \
+  >     echo "key: 3"; echo "value: c"; \
+  >     echo "key: 4"; echo "value: d"
+  >   context
+  >   context
+  >   key: 1
+  >   value: a
+  >   key: 2
+  >   value: b
+  >   key: 3
+  >   value: * (glob)
+  >   key: 4
+  >   value: * (glob)
+  > EOF
+  $ rt test-failure-globs.t
+  
+  --- $TESTTMP/test-failure-globs.t
+  +++ $TESTTMP/test-failure-globs.t.err
+  @@ -2,10 +2,10 @@
+     context
+     context
+     key: 1
+  -  value: a
+  +  value: * (glob)
+     key: 2
+  -  value: b
+  +  value: * (glob)
+     key: 3
+  -  value: * (glob)
+  +  value: c
+     key: 4
+  -  value: * (glob)
+  +  value: d
+  
+  ERROR: test-failure-globs.t output changed
+  !
+  Failed test-failure-globs.t: output changed
+  # Ran 1 tests, 0 skipped, 1 failed.
+  python hash seed: * (glob)
+  [1]
+  $ rm test-failure-globs.t
+
 test diff colorisation
 
 #if no-windows pygments
@@ -374,6 +420,7 b' test --xunit support'
 
   $ cat .testtimes
   test-empty.t * (glob)
+  test-failure-globs.t * (glob)
   test-failure-unicode.t * (glob)
   test-failure.t * (glob)
   test-success.t * (glob)