util: enhance `nullcontextmanager` to be able to return __enter__ result
This makes its functionality and signature equivalent to Python 3.7’s
contextlib.nullcontext().
# In most cases, the mercurial repository can be read by the bundled hg, but
# that isn't always true because third-party extensions may change the store
# format, for example. In which case, the system hg installation is used.
#
# We want to use the hg version being tested when interacting with the test
# repository, and the system hg when interacting with the mercurial source code
# repository.
#
# The mercurial source repository was typically orignally cloned with the
# system mercurial installation, and may require extensions or settings from
# the system installation.
if [ -n "$HGTESTEXTRAEXTENSIONS" ]; then
for extension in $HGTESTEXTRAEXTENSIONS; do
extraoptions="$extraoptions --config extensions.$extension=!"
done
fi
syshg () {
(
syshgenv
exec hg "$@"
)
}
# Revert the environment so that running "hg" runs the system hg
# rather than the test hg installation.
syshgenv () {
. "$HGTEST_RESTOREENV"
HGPLAIN=1
export HGPLAIN
}
# The test-repo is a live hg repository which may have evolution markers
# created, e.g. when a ~/.hgrc enabled evolution.
#
# Tests may be run using a custom HGRCPATH, which do not enable evolution
# markers by default.
#
# If test-repo includes evolution markers, and we do not enable evolution
# markers, hg will occasionally complain when it notices them, which disrupts
# tests resulting in sporadic failures.
#
# Since we aren't performing any write operations on the test-repo, there's
# no harm in telling hg that we support evolution markers, which is what the
# following lines for the hgrc file do:
cat >> "$HGRCPATH" << EOF
[experimental]
evolution = createmarkers
EOF
# Use the system hg command if the bundled hg can't read the repository with
# no warning nor error.
if [ -n "`hg id -R "$TESTDIR/.." 2>&1 >/dev/null`" ]; then
alias testrepohg=syshg
alias testrepohgenv=syshgenv
else
alias testrepohg="hg $extraoptions"
alias testrepohgenv=:
fi