Allow "nonexistent version" test to work without brew

Currently, this test fails if Homebrew isn't present as it expects a
Homebrew-specific output. This commit varies the expected output based
on whether Homebrew is installed.

This patch was originally created for the Debian package for ruby-build:
https://salsa.debian.org/ruby-team/ruby-build/-/blob/607093e5198cc75ffa8e9a3b551843be5f2f6d93/debian/patches/0001-Fix-nonexistent-version-test-to-work-regardless-of-e.patch

test/rbenv.bats

@@ -94,7 +94,8 @@ OUT
 
   run rbenv-install 1.9.3
   assert_failure
-  assert_output <<OUT
+  (
+    cat <<OUT
 ERROR
 
 The following versions contain \`1.9.3' in the name:
@@ -103,10 +104,19 @@ The following versions contain \`1.9.3' in the name:
 
 See all available versions with \`rbenv install --list-all'.
 
-If the version you need is missing, try upgrading ruby-build:
-
-  git -C ${BATS_TEST_DIRNAME/$HOME\//~/}/.. pull
 OUT
+    here="${BATS_TEST_DIRNAME}/.."
+    echo -n "If the version you need is missing, try upgrading ruby-build"
+    if [ "$here" != "${here#$(brew --prefix 2>/dev/null)}" ]; then
+      printf ":\n\n"
+      echo "  brew update && brew upgrade ruby-build"
+    elif [ -d "${here}/.git" ]; then
+      printf ":\n\n"
+      echo "  git -C ${here} pull"
+    else
+      printf ".\n"
+    fi
+  ) | assert_output
 
   unstub brew
   unstub ruby-build