Guys only: what does it mean when a guy touches you like this?

So I saw my ex today for the first time in 6 months. I was sitting in a chair in his office and he was walking past me to grab something and he did a little squuze/massage on the top of my scalp when he walked past. Is this a sign of affection?
Guys only: what does it mean when a guy touches you like this?
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