I hit this issue trying to sync websockets WPT:

- https://ews-build.webkit.org/#/builders/4/builds/9571
- https://ews-build.webkit.org/#/builders/4/builds/9576

Output:

using PTY: False
program finished with exit code 0
elapsedTime=0.026877
git remote set-url annevk https://github.com/annevk/WebKit.git
 in dir /Volumes/Data/worker/watchOS-9-Build-EWS/build (timeout 600 secs)
 watching logfiles {}
 argv: [b'git', b'remote', b'set-url', b'annevk', b'https://github.com/annevk/WebKit.git']
 using PTY: False
program finished with exit code 0
elapsedTime=0.016769
git fetch annevk eng/Synchronize-websockets-WPT
 in dir /Volumes/Data/worker/watchOS-9-Build-EWS/build (timeout 600 secs)
 watching logfiles {}
 argv: [b'git', b'fetch', b'annevk', b'eng/Synchronize-websockets-WPT']
 using PTY: False
From https://github.com/annevk/WebKit
 * branch                      eng/Synchronize-websockets-WPT -> FETCH_HEAD
 * [new branch]                eng/Synchronize-websockets-WPT -> annevk/eng/Synchronize-websockets-WPT
program finished with exit code 0
elapsedTime=1.427224
git checkout -b eng/Synchronize-websockets-WPT
 in dir /Volumes/Data/worker/watchOS-9-Build-EWS/build (timeout 600 secs)
 watching logfiles {}
 argv: [b'git', b'checkout', b'-b', b'eng/Synchronize-websockets-WPT']
 using PTY: False
Switched to a new branch 'eng/Synchronize-websockets-WPT'
program finished with exit code 0
elapsedTime=0.013735
git cherry-pick HEAD..remotes/annevk/eng/Synchronize-websockets-WPT
 in dir /Volumes/Data/worker/watchOS-9-Build-EWS/build (timeout 600 secs)
 watching logfiles {}
 argv: [b'git', b'cherry-pick', b'HEAD..remotes/annevk/eng/Synchronize-websockets-WPT']
 using PTY: False
error: The following untracked working tree files would be overwritten by merge:
	LayoutTests/imported/w3c/web-platform-tests/websockets/Send-unpaired-surrogates.any.worker.html
Please move or remove them before you merge.
Aborting
fatal: cherry-pick failed
program finished with exit code 128
elapsedTime=2.544757