This reapplies #5048, because it somehow got reverted during a refactoring (I believe).

To prevent it from happening again in future, I added a comment in the code.

This also:

• Expand -1 into --max-count=1 (long options are always preferred for better readability)

• Add -- to prevent file names who looks like git options to clash

• Check if the file exists before issuing git and return a proper error message

  • git log is known to return exit code 0 but no output in some cases, such as when using -- and the file does not exist
  • If preferred, I can instead check if stdout is empty rather than proactively checking the file