dispatch: adjust ui.flush() timing to stabilize test-blackbox.t
Without this change, dispatch.dispatch() could return before flushing all
stdio data. This means chg stdio would print data after receiving the result
code.
--- tests/test-blackbox.t
+++ tests/test-blackbox.t.err
@@ -354,13 +354,13 @@
> EOF
$ hg log --debug
removing $TESTTMP/gone/.hg
- warning: cannot write to blackbox.log: $ENOENT$ (no-windows !)
warning: cannot write to blackbox.log: $TESTTMP/gone/.hg/blackbox.log: $ENOTDIR$ (windows !)
$ cd ..
blackbox should disable itself if track is empty
$ hg --config blackbox.track= init nothing_tracked
+ warning: cannot write to blackbox.log: $ENOENT$
$ cd nothing_tracked
$ cat >> .hg/hgrc << EOF
> [blackbox]
syntax: glob
*.elc
*.tmp
*.orig
*.rej
*~
*.mergebackup
*.o
*.so
*.dll
*.exe
*.pyd
*.pyc
*.pyo
*$py.class
*.swp
*.prof
*.zip
\#*\#
.\#*
tests/artifacts/cache/big-file-churn.hg
tests/.coverage*
tests/.testtimes*
tests/.hypothesis
tests/hypothesis-generated
tests/annotated
tests/exceptions
tests/*.err
tests/htmlcov
build
contrib/chg/chg
contrib/hgsh/hgsh
contrib/vagrant/.vagrant
dist
packages
doc/common.txt
doc/*.[0-9]
doc/*.[0-9].txt
doc/*.[0-9].gendoc.txt
doc/*.[0-9].{x,ht}ml
MANIFEST
MANIFEST.in
patches
mercurial/__modulepolicy__.py
mercurial/__version__.py
mercurial/hgpythonlib.h
mercurial.egg-info
.DS_Store
tags
cscope.*
.idea/*
.asv/*
.pytype/*
.mypy_cache
i18n/hg.pot
locale/*/LC_MESSAGES/hg.mo
hgext/__index__.py
rust/target/
rust/*/target/
# Generated wheels
wheelhouse/
syntax: regexp
^\.pc/
^\.(pydev)?project
# hackable windows distribution additions
^hg-python
^hg.py$