Backport #23010.
Fix#23000.
The bug was introduced in #22633, and it seems that it has been noticed:
https://github.com/go-gitea/gitea/pull/22633#discussion_r1095395359 .
However, #22633 did nothing wrong, the logic should be "check if they is
admin only when `force` is true".
So we should provide the `ForceMerge` when merging from UI.
After this, an admin can also send a normal merge request with
`ForceMerge` false. So it fixes a potential bug: if the admin doesn't
want to do a force merge, they just see the green "Merge" button and
click it. At the same time, the status of the PR changed, and it
shouldn't be merged now, so the admin could send an unexpected force
merge.
In addition, I updated `ForceMerge *bool` to `ForceMerge bool`, I don't
see the reason to use a pointer.
And fixed the logic of CheckPullMergable to handle auto merge and force
merge correctly.
* Fixes issue #19603 (Not able to merge commit in PR when branches content is same, but different commit id)
* fill HeadCommitID in PullRequest
* compare real commits ID as check for merging
* based on @zeripath patch in #19738
Jason Song
wxiaoguang
Yarden Shoham
Ing. Jaroslav Šafka
6543