Fixed simulate diff mode not reporting a removal with a version

[djbclark]

--simulate=diff dropped a removal with a version unless it cancelled a recorded install of the same version. The else branch meant for "a different version of this package is about to be installed" also caught the common case where nothing was recorded as installed, so removing version 1.0 of a present package vanished from the diff report while --simulate=manifest still said "would be absent". One-line fix (else → else if (inst_record != NULL)), a regression test that fails without it, and a test for the case the branch still covers:

$ tests/unit/simulate_mode_test      # without the fix
ERROR: simulate_mode_test.c:114 Failure!
test_diff_removal_with_version: Test failed.
1 out of 5 tests failed!
$ tests/unit/simulate_mode_test      # with the fix
All 5 tests passed

Fork CI: djbclark#44

AI-assisted. I can't vouch for the C syntax beyond a basic level, but I did look at the logic and it seemed sound.

🤖 Generated with Claude Code

[larsewi]

Thanks 🚀 Could you change it to use StringContains()? It reads a bit better.

[larsewi]

@cf-bottom Jenkins please :)

[cf-bottom]

Sure, I triggered a build:

Jenkins: https://ci.cfengine.com/job/pr-pipeline/14818/

Packages: http://buildcache.cfengine.com/packages/testing-pr/jenkins-pr-pipeline-14818/