Tested unconventionally:
- Created a folder in Desktop named
abc– timestamp 12:00:00 - Created another folder named
abcsomewhere else after a second – timestamp 12:00:01 - Copied second one and paste on desktop > Want to replace? > Yes
- Folder
abc(first one) replaced with folderabc(second one)
Result: Timestamp stayed same as previous 12:00:00
- Downloaded Theme Check’s older version
- Unziped in
plugins/directory, and checked the timestamp 12:00:00 - Visited
wp-admin/update-core.phpso the new version warning appears - Select ‘Theme Check’ to update, and hit Update Plugins button
- Plugin successfully updated. Checked the folder properties of ‘Theme Check’
Result: Timestamp is new 12:01:37
I tried some other methods, opening the plugins/ directory in another window and observing what’s happening behind. Seen no replacement.
So, it’s confirmed from me that,
- WordPress create
.maintenancefile in root first, - then download the
.zipfile first in temporary location or memory, - then delete the older version’s folder,
- then unzip the new version there, and
- finally delete the
.maintenancefile from the root
No replacement – Confirmed. 🙂