Show a spinner (whatever) while loading

[dimateos]

The list/graph of commits should be discarded/hidden when a new list/graph is being loaded.
Should also show a placeholder loader spinner or something, but at the very least discard the shown ones:

In the following GIF the loading is fast but sometimes (e.g. large repo or workspace startup) it can take several seconds where the combo box shows the newly selected repo WITH the commits/graph from the previous.

Actually, you can scroll and select commits from the previous while the new is yet to be loaded and then you get these popup errors:

^ In this case I only show the graph for privacy, and you can only see the loading spinner from mhutchie.git-graph for a split second

There could be an option to toggle this in case users want to avoid the empty view popping between loads. IMO not worth the effort and this should be forced as the current behavior can leads to the mentioned errors.

Not high priority, but good UX improvement and avoids edge case errors.

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Related to initial repo info queries mentioned in #93 and extending to #71
The current issue is about every time the graph for a specific repo is requested, but I guess if there is a placeholder while loading then:

• Use it at the initial load too, not only when switching between repos (discarding current graph)
  • Similar to top-right reload button rotation
• Here the spinner/loader could transition to X error when there are issues, instead of popups (but complementing console/log errors)
  • When the error is about empty repo/not loaded yet, hint the user to "Refresh" to retry
  • NOTE:: in the current issues mentioned the view is empty forever and the user cannot "Refresh" (even the button is spinning constantly)

Regards! many times today :)