git show with copying file as custom action

[Martin Widmer]

We want to define a custom action, which copies a specific file from a selected commit to a temporary file,

The goal is to be able to then merge/compare the files using an external tool, which unfortunately cannot be called from command line. (Specifically: Codesys)

The solution we were trying so far is the following custom action:
Script to run: C:\Program Files\Git\bin\git.exe
Parameters: show $SHA:./test.project > ./test_old.project

However, this does not seem to work, even though copying the resulting command to the git terminal works just fine...
The resulting message was at first something about " > " being ambiguos, but somehow it in by now just "Completed with errors, see above."