Merge pull request #25387 from yuwata/core-fix-gc-logic

core: fix logic of merging units

diff --cc src/core/unit.c
Simple merge

diff --cc test/units/testsuite-26.sh
index 0fe0d9b0d95bb25fc1bec4bf93fbc30c41136eea,a8e7a5abaa7d80f97ab26b05f61bccd8466df9ef..2e0350aabe394aa8fd152fcec481a139d32311d3
--- 1/test/units/testsuite-26.sh
--- 2/test/units/testsuite-26.sh
+++ b/test/units/testsuite-26.sh
@@@ -4,15 -3,20 +4,23 @@@
  set -eux
  set -o pipefail
  
+ # shellcheck source=test/units/assert.sh
+ . "$(dirname "$0")"/assert.sh
+ 
+ : >/failed
+ 
  at_exit() {
      if [[ -v UNIT_NAME && -e "/usr/lib/systemd/system/$UNIT_NAME" ]]; then
 -        rm -fv "/usr/lib/systemd/system/$UNIT_NAME"
 +        rm -fvr "/usr/lib/systemd/system/$UNIT_NAME" "/etc/systemd/system/$UNIT_NAME.d" "+4"
      fi
+ 
+     rm -f /etc/init.d/issue-24990
+     return 0
  }
  
 +# shellcheck source=test/units/assert.sh
 +. "$(dirname "$0")"/assert.sh
 +
  trap at_exit EXIT
  
  # Create a simple unit file for testing