if file isn't available (refactor/move) then offer to show history

[championswimmer]

So simple example here

https://github.com/championswimmer/vuex-module-decorators/blob/master/test/getmodule.ts

^^ this page is not available as I have moved this file. but that link is shared many places

https://github.com/championswimmer/vuex-module-decorators/commits/master/test/getmodule.ts

^^ this on the other hand is a great place to see what the file was last time it existed

So when we go to

https://github.com/{org}/{repo}/blob/{branch}/path/to/file.ext

In the error page show a link to

https://github.com/{org}/{repo}/commits/{branch}/path/to/file.ext

[clarkbw]

I think this is a duplicate of #900