Attempt to fix docs publishing script

The problem is that it would have pushed production
docs to the production branch.  That's no good because
the docs are only served from master.

Author: craigfowler

Tools/appveyor-publish-docs-site.ps1

@@ -15,6 +15,9 @@ else {
     exit 0
 }
 
+Write-Host "Switching to a temp branch"
+git checkout -b temp/publish-docs
+
 Write-Host "Publishing the docs site to $BaseDir"
 
 Write-Host "Clearing $BaseDir ..."
@@ -51,7 +54,14 @@ git add --all docs/
 Write-Host "Creating commit"
 git commit -m "Auto-publish docs website [skip ci]"
 
-if($Env:APPVEYOR -eq "True") {
+if($Env:APPVEYOR -eq "True" -and $Env:APPVEYOR_REPO_BRANCH -eq "production") {
+    Write-Host "Pushing to origin"
+    git checkout master
+    git pull
+    git merge temp/publish-docs --no-ff -m "Merge newly-published docs [skip ci]"
+    git push origin master
+}
+elseif ($Env:APPVEYOR -eq "True") {
     Write-Host "Pushing to origin"
-    git push origin HEAD:$Env:APPVEYOR_REPO_BRANCH
+    git push origin temp/publish-docs:master
 }