Delete untracked tags on fetch step

[stsewd]

Currently, if the user deletes a tag, it needs to wipe the environment for this change be reflected in their version list.

There are some solutions to delete untracked tags (require more than 2 commands). But I found that the newest version of git has the --prune-tags option, which is used as git fetch --prune --prune-tags (git >2.17). We need to update git on the servers (we use 2.7.4) and change the fetch command. Or we can find a way to wipe the environment if we detect something like this case.

Raised in #3913 (comment)

[humitos]

I think we can implement the command you mentioned here very soon since we are migrating our servers to Ubuntu 18.04 which includes 2.17.1 by default: https://packages.ubuntu.com/bionic/git

The PR needed for this should be very simple and shouldn't have any secondary effect :)

I'm 👍 on adding the --prune-tags to our current command.

[agjohnson]

Blocking until .com update to 18.04

[ericholscher]

Believe that #4811 didn't totally fix this. Reopening for now.

[stsewd]

So, tags are being deleted, the sync version bug is because of another problem, I opened #4875