[Feature Request] Enable fetch refspec editing in repo settings

[ablekhman]

Add fetch refspec editing in the "Settings for this repository" dialog. Right now the only way to edit fetch refspec is to open .git/config directly.

[DanPristupov]

Right now the only way to edit fetch refspec is to open .git/config directly.

Correct. There is nothing wrong with that. Not every git setting needs a GUI.