Auto merge of #23112 - servo:jdm-patch-31, r=Manishearth

Use consistent local branch name for WPT sync.

This avoids the problem of the WPT sync running two commands on different dates and therefore not finding the previously created branch.

- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #23052

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etc/ci/update-wpt-checkout

@@ -11,7 +11,8 @@ set -o pipefail
 REMOTE_NAME=sync-fork
 LOG_FILE=test-wpt.log
 CURRENT_DATE=$(date +"%d-%m-%Y")
-BRANCH_NAME="wpt_update_${CURRENT_DATE}"
+BRANCH_NAME="wpt_update"
+REMOTE_BRANCH_NAME="wpt_update_${CURRENT_DATE}"
 
 export GIT_AUTHOR_NAME="WPT Sync Bot"
 export GIT_AUTHOR_EMAIL="josh+wptsync@joshmatthews.net"
@@ -94,7 +95,7 @@ function unsafe_open_pull_request() {
     AUTH="${WPT_SYNC_USER}:${WPT_SYNC_TOKEN}"
     UPSTREAM="https://${AUTH}@github.com/${WPT_SYNC_USER}/servo.git"
     git remote add "${REMOTE_NAME}" "${UPSTREAM}" || return 2
-    git push -f "${REMOTE_NAME}" "${BRANCH_NAME}" &>/dev/null || return 3
+    git push -f "${REMOTE_NAME}" "${BRANCH_NAME}:${REMOTE_BRANCH_NAME}" &>/dev/null || return 3
 
     # Prepare the pull request metadata.
     BODY="Automated downstream sync of changes from upstream as of "
@@ -103,7 +104,7 @@ function unsafe_open_pull_request() {
     cat <<EOF >prdata.json || return 4
 {
   "title": "Sync WPT with upstream (${CURRENT_DATE})",
-  "head": "${WPT_SYNC_USER}:${BRANCH_NAME}",
+  "head": "${WPT_SYNC_USER}:${REMOTE_BRANCH_NAME}",
   "base": "master",
   "body": "${BODY}",
   "maintainer_can_modify": true