Don't display "View file ((head|base))" if the file doesn't exist

[ijsnow]

We shouldn't display a link to open a file that doesn't exist at a revision. Phabricator has this built in here but this should be re-implemented in a more shareable way.

[sqs]

This occurs on a diff when a file was added (file does not exist in base) or deleted (file does not exist in head).

[hemal7735]

Hi @ijsnow , can you add a GIF or steps for reproducing the issue?

[ijsnow]

Hi, sorry won’t be at my computer until later today.

You can reproduce by finding or making a revision or commit where a file was either added or deleted.

I modified the link above so you can see how I’ve done this for Phabricator. Note that this issue is for implementing this in a sharable way, not just for GitHub so changes should be in libs/code_intelligence

[github-actions]

Heads up @Joelkw @felixfbecker - the "team/extensibility" label was applied to this issue.