Merge fort-nix/nix-bitcoin#545: test/lib/create-git-repo: fix variable quoting

49e30f7172 test/lib/create-git-repo: fix empty var expansion (Erik Arvstedt)

Pull request description:

ACKs for top commit:
  jonasnick:
    ACK 49e30f7172

Tree-SHA512: 321f01bd8674e7cc91718e9799e3175cb640feb42ebac90588a60cdbe160b705aac4effa4cc229adc41c062c3cdf7ad90317a4dde90665d71141016faf2ce43a

test/lib/create-git-repo.sh

@@ -2,14 +2,14 @@
 (
   # shellcheck disable=SC2154,SC2164
   cd "$scriptDir/.."
-  amend=--amend
+  amend=(--amend)
 
   if [[ ! -e .git ]] || ! git rev-parse HEAD 2>/dev/null; then
     git init
-    amend=
+    amend=()
   fi
   git add .
   if ! git diff --quiet --cached; then
-    git commit -a "$amend" -m -
+    git commit -a "${amend[@]}" -m -
   fi
 ) >/dev/null