Rendering the git graph on the server means that we can properly track flows and switch from the Canvas implementation to a SVG implementation.

* This implementation provides a 16 limited color selection
* The uniqued color numbers are also provided
* And there is also a monochrome version
*In addition is a hover highlight that allows users to highlight commits on the same flow.

Closes #12209

Signed-off-by: Andrew Thornton art27@cantab.net
Co-authored-by: silverwind <me@silverwind.io>

* Ensure that git commit tree continues properly over the page

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Avoid generating strings when skipping

Signed-off-by: Andrew Thornton <art27@cantab.net>

* skip initial non-commit-lines

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lauris BH <lauris@nix.lv>