* add submodule on tree-sitter-git-diff
* add git-diff highlights
* inject git-diff into git-commit
* update tree-sitter-git-commit with fix for bad diff case
* add git-diff to language support docs
* include-children in diff injections
This ensures that children nodes of $.message are included in the
injection, such as $.user or issue/pr numbers. Without this change,
diffs containing '#' or '@' characters can trip up the injection and
be parsed separately.
See https://github.com/helix-editor/helix/pull/1373#issuecomment-1001215629
* set diff language's scope as source.diff
