If MovePage::move() has an exception during a database operation it fails to move the file back to the original location. Since the database operations are wrapped in a transaction the file move can be moved down to trigger the transaction to rollback if the file fails to move.
See also: T153565
Change 478237 had a related patch set uploaded (by Alexia; owner: Alexia):
[mediawiki/core@master] Cancel the transaction if the file fails to move. This prevents losing files when there is a database error.
Change 478237 merged by jenkins-bot:
[mediawiki/core@master] Cancel the transaction if the file fails to move. This prevents losing files when there is a database error.
Change 478749 had a related patch set uploaded (by Alexia; owner: Alexia):
[mediawiki/core@master] Can't call escaped() on a string.
Change 478749 merged by jenkins-bot:
[mediawiki/core@master] Can't call escaped() on a string.