[Feature] Configurable location for `sourcegit.settings` file

[codarch]

It would be great if the application was able to store repository-specific configuration settings outside of the repository (the .git folder) and keep the repository itself clean from product-specific files. Git clients tend to treat the repository as if it were their own territory and put their arbitrary data there. That data have nothing to do with core Git files and (in my opinion) do not really belong there.

Not to mention that this practice might cause issues on a long-term period if the format of the client configuration changes (I expect future Git versions to have backward compatible changes only, but Git clients may change at a faster pace, more dynamically).

Therefore I suggest introducing an option to store repository-specific settings in a centralized manner, for instance in the SourceGit application data directory.

Nonetheless this is a great product, thanks for the efforts of all contributors!

[love-linger]

• The original intention of the .git directory is to store repository-related configurations, current states and datas, and the git process does not care about files that it did not create or need.
• As far as I know, currently many tools store their own repository-related configurations and datas in the .git directory, including but not limited to:
  • git-lfs stores its blob data in the .git/lfs-objects directory.
  • The well-known GIT client SourceTree stores settings for individual repositories in the .git/sourcetreeconfig.json file.
  • Another well-known GIT client (which I also liked before) fork also stores repository-related configurations and datas in this directory.
  • The well-known 3D engine Unreal Engine has implemented their own large file management tool - GitDependencies which also stores its own data in the .git/ue-depends directory.
• Storing in this directory has some advantages, including but not limited to:
  • Easier to locate the configuration file.
  • When the local repository does not exist, such as when it is deleted, its configuration data is naturally deleted and no additional detection and management is needed.
  • The configuration data is not affected by the local working copy and will not be accidentally deleted due to git operations.