Allow changing the similarity index threshold

Sometimes a file gets renamed and also changed a lot (e.g.: when converting a Java class to Groovy or Kotlin or vice versa).

If this "a lot" exceeds the 50% default similarity index computed by Git, the diff dialog shows 2 separate entries (delete+add) rather than a single rename/update one, and that makes checking differences harder and more cumbersome.

It would be nice if TortoiseGit could expose the threshold for the similarity index, either in the diff dialog or maybe as a numeric parameter in the advanced settings section.

What version of TortoiseGit and Git are you using? On what operating system?

2.6.0 / Windows 10

Please provide any additional information below.

I'm referring to the -M or --find-renames options documented here: https://git-scm.com/docs/git-diff

This somewhat related to enhancement 3219