Error: Command failed due to missing milestone.
aarch64 backend fails to optimize vector equal as bitmask operation · Issue #66317 · llvm/llvm-project (github.com) seems to have similar issue (maybe it’s confused by quoted code or something?).
It appears it thought that I wanted to create a pull request? Assertion `Denominator > 0 && “Denominator cannot be 0!”’ failed. · llvm/llvm-project@7472490 (github.com)
The action file looks for /branch as a command, but a link to llvm/lib/Analysis/BranchProbabilityInfo.cpp is enough to trigger it.
https://github.com/llvm/llvm-project/actions/runs/6187781308/workflow#L73
Perhaps the command check should be tighter, by requiring a space following it or requiring to be at the start of a line, something like that?
Github does not support regex in if - there are countless people desperately asking for that feature on SO & google 
It seems the best we can do is something like GitHub Actions CI Conditional Regex - Stack Overflow
Requiring a space makes sense and should significantly reduce the number of false-positives without any false-negatives. Also, surprising that it’s case-insensitive by default (if there is even an option to make it case-sensitive).
[github] Make branch workflow more robust by danilaml · Pull Request #66781 · llvm/llvm-project
Added a check for space (I hope it won’t be ignored by contains if it does something stupid like .strip()-ing it’s content).