Overwriting changes from the editing conflict screen also abandons any additional changes made after the conflict was detected

If an update is performed on an old version of a page, then Confluence attempts to merge the changes. If the changes cannot be merged by Confluence then it asks the user to do it. (Not too well, see CONF-11529). If this merge takes the user some time, and more changes are made in the meantime before the user saves again, the additional changes are lost, and no warning is given.

Suppose you have a page with lots of collaboration in a short time. Eg a meeting minutes page. The following steps cause data to be lost with no report.

1. UserA starts editing the page.
2. UserB starts editing the page.
3. UserB adds a new line with some content to the end of the page and saves. The change is committed.
4. UserA adds a new line with some content to the end of the page and saves. The change conflicts with UserB's change so he is given a merge page.
5. UserC starts editing the page.
6. UserC adds a new line with some content to the end of the page and saves. The change is committed successfully.
7. UserA dutifully adds UserB's line into the editor before or after his own, and clicks Overwrite. The change is committed successfully. No merge with UserC's change is performed.

The end result is that despite UserA doing the right thing and properly merging the changes, UserC's changes are completely lost and nobody will ever know. (Note, there don't really need to be 3 users, UserB could just make more changes while UserA is merging the first ones).

Suggested fix.

Overwriting should be subject to another merge check for any changes made since the last merge was calculated.