tools: Avoid double-tagging in wporg SVN (#28437)

The command used to tag a release in SVN has an unfortunate failure
modde if the tag already exists: instead of simply failing, it will
create a `trunk` directory inside the tag.

This PR does two things to try to avoid this situation:

* The manual `deploy-to-svn.sh` script will now confirm if someone tries
  to run it on a plugin that is set up for auto-publish.
* Both that and the auto-publish will abort if they detect the tag
  already exists (but note this check is subject to races).

.github/files/gh-wp-svn-autopublish/files/wp-svn-autopublish.sh

@@ -37,9 +37,14 @@ svn up trunk
 echo '::endgroup::'
 
 echo "::group::Checking out SVN tags (shallowly)"
-svn up tags --depth=empty
+svn up tags --depth=immediates
 echo '::endgroup::'
 
+if [[ -e "tags/$TAG" ]]; then
+	echo "::error::Tag $TAG already exists in SVN. Aborting."
+	exit 1
+fi
+
 echo "::group::Deleting everything in trunk except for .svn directories"
 find trunk ! \( -path '*/.svn/*' -o -path "*/.svn" \) \( ! -type d -o -empty \) -delete
 [[ -e trunk ]] || mkdir -p trunk # If there were no .svn directories, trunk itself might have been removed.

tools/deploy-to-svn.sh

@@ -84,6 +84,12 @@ if [[ -z "$WPSLUG" ]]; then
 fi
 $FAIL && exit 1
 
+if jq -e '.extra["wp-svn-autopublish"] // false' "$PLUGIN_DIR/composer.json" &>/dev/null; then
+	yellow "$PLUGIN_NAME is set up to automatically publish to WordPress.org via GitHub Actions."
+	yellow $'\e[1mIf you run this script in addition to the auto-publish, you\'ll likely wind up with a broken tag (see https://github.com/Automattic/jetpack/issues/28400).'
+	proceed_p '' 'Really publish to SVN manually?'
+fi
+
 # Check build dir.
 if [[ -z "$BUILD_DIR" ]]; then
 	TMPDIR="${TMPDIR:-/tmp}"
@@ -124,9 +130,13 @@ printf "\r\e[K"
 success "Done!"
 
 info "Checking out SVN tags shallowly to $DIR/tags"
-svn -q up tags --depth=empty
+svn -q up tags --depth=immediates
 success "Done!"
 
+if [[ -e "tags/$SVNTAG" ]]; then
+	die "Tag $SVNTAG already exists in SVN. Aborting."
+fi
+
 info "Deleting everything in trunk except for .svn directories"
 find trunk ! \( -path '*/.svn/*' -o -path "*/.svn" \) \( ! -type d -o -empty \) -delete
 [[ -e trunk ]] || mkdir -p trunk # If there were no .svn directories, trunk itself might have been removed.