tests: quote variable passed to shell test command

tests/helpers-testrepo.sh

@@ -1,60 +1,60 b''
 # 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 $HGTESTEXTRAEXTENSIONS ]; then
+if [ -n "$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