Is it possible to add a refactoring flag to geany in that:

if it is in refactoring mode than we can reformat the original code(along with my new code changes) based on newline/tab-space/rules in geany at either editing time, or saving time, or both.

if it is in non-refactoring mode, then our new added code can follow whatever format rules defined by geany, however, the previous code base, even though its format is messy, we don't reformat them to avoid a noisy diff file. For example, I have a 1000 lines of messy.c code, I added 100 lines on top of that, only the 100 lines will have new formats but the old 1000 lines will not be reformatted by geany in anyway, so my git-diff/svn-diff do not lose focus when old code is involved, which is the majority of the time these days.

I see no editor can do this