[enhancement] Add 'invalid upstream' indicators in log-graph

[goran-w]

The recent change to "merge" the local branch and upstream indicators in the log-graph (when they coincide) opens up for a useful way to also indicate 'invalid upstream' there (when applicable). There's already an indicator (orange warning triangle) for that in the Local Branches list, but having a similar indicator also in the log-graph would be helpful.

Existing (valid-)upstream indicator :

Quick mockup of how the suggested invalid-upstream indicator could look :

[love-linger]

The purpose of CommitRefsPresenter is crystal clear: to let users instantly see which refs point to the target commit.

In your mockup image, it tells user that there's a local branch named files_preserve_tree_state that points to the target commit. There are no errors with that commit.

[love-linger]

If we add the warning icon in that place, it means there's another ref (origin/files_preserve_tree_state in your mockup image) that points to the target commit but something wrong with it - This is wrong because there is not such a ref (origin/files_preserve_tree_state in your mockup image) that points the target commit actually

[love-linger]

If you really want it and implement it in your own fork, I suggest to use:

| <icon> | <branch_name> <warning_icon> | <other_remotes> | ....

instead of:

| <icon> | <branch_name> | <warning_icon> | <other_remotes> | ....

[goran-w]

If you really want it and implement it in your own fork, I suggest to use:
| <icon> | <branch_name> <warning_icon> | <other_remotes> | ....

Sure, that would be clearer! It's still a helpful indicator, that would make the ref picture more complete and also more consistent with the corresponding ref in the sidebar!