Suppress SC2086 where word splitting is intended

This suppresses ShellCheck SC2016, "Double quote to prevent
globbing and word splitting," on the command in the version check
script that expands $config_opts to build the "-c ..." arguments.

It also moves the code repsonsible for getting the latest tag,
which this is part of, into a function for that purpose, so it's
clear that building config_opts is specifically for that, and so
that the code is not made harder to read by adding the ShellCheck
suppression comment.

(The suppression applies only to the immediate next command.)

check-version.sh

@@ -10,6 +10,13 @@ trap 'echo "$0: Check failed. Stopping." >&2' ERR
 readonly version_path='VERSION'
 readonly changes_path='doc/source/changes.rst'
 
+function get_latest_tag() {
+    local config_opts
+    config_opts="$(printf ' -c versionsort.suffix=-%s' alpha beta pre rc RC)"
+    # shellcheck disable=SC2086  # Deliberately word-splitting the arguments.
+    git $config_opts tag -l '[0-9]*' --sort=-v:refname | head -n1
+}
+
 echo 'Checking current directory.'
 test "$(cd -- "$(dirname -- "$0")" && pwd)" = "$(pwd)"  # Ugly, but portable.
 
@@ -26,8 +33,7 @@ test -z "$(git status -s --ignore-submodules)"
 
 version_version="$(cat "$version_path")"
 changes_version="$(awk '/^[0-9]/ {print $0; exit}' "$changes_path")"
-config_opts="$(printf ' -c versionsort.suffix=-%s' alpha beta pre rc RC)"
-latest_tag="$(git $config_opts tag -l '[0-9]*' --sort=-v:refname | head -n1)"
+latest_tag="$(get_latest_tag)"
 head_sha="$(git rev-parse HEAD)"
 latest_tag_sha="$(git rev-parse "${latest_tag}^{commit}")"