test: explicitly "add" file before some commit in test-rollback.t
`hg commit -A` will revert the `hg addremove` step if the commit fails. However
`hg rollback` currently does not.
We are about to improve internal consistency around transaction and dirstate and the behavior of `hg rollback` will align on the other behavior in the process.
Before doing so, we make sure the test is using a separate call to `hg add` to
avoid the test scenario to be affected by that future change.
note: the behavior change for `hg rollback` seems fine as it affect a niche
usecase and `hg rollback` usage have been strongly discouraged for a while.
Our full contribution guidelines are in our wiki, please see:
https://www.mercurial-scm.org/wiki/ContributingChanges
If you just want a checklist to follow, you can go straight to
https://www.mercurial-scm.org/wiki/ContributingChanges#Submission_checklist
If you can't run the entire testsuite for some reason (it can be
difficult on Windows), please at least run `contrib/check-code.py` on
any files you've modified and run `python contrib/check-commit` on any
commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).