Merge branch 'jk/epipe-in-async' into maint

Handling of errors while writing into our internal asynchronous
process has been made more robust, which reduces flakiness in our
tests.

* jk/epipe-in-async:
  t5504: handle expected output from SIGPIPE death
  test_must_fail: report number of unexpected signal
  fetch-pack: ignore SIGPIPE in sideband demuxer
  write_or_die: handle EPIPE in async threads

t/t5504-fetch-receive-strict.sh

@@ -101,7 +101,10 @@ test_expect_success 'push with receive.fsckobjects' '
 		git config transfer.fsckobjects false
 	) &&
 	test_must_fail ok=sigpipe git push --porcelain dst master:refs/heads/test >act &&
-	test_cmp exp act
+	{
+		test_cmp exp act ||
+		! test -s act
+	}
 '
 
 test_expect_success 'push with transfer.fsckobjects' '

t/test-lib-functions.sh

@@ -617,7 +617,7 @@ test_must_fail () {
 		return 0
 	elif test $exit_code -gt 129 && test $exit_code -le 192
 	then
-		echo >&2 "test_must_fail: died by signal: $*"
+		echo >&2 "test_must_fail: died by signal $(($exit_code - 128)): $*"
 		return 1
 	elif test $exit_code -eq 127
 	then