Fix `View File` button link if branch deleted on pull request files pages

[metiftikci]

as title

[metiftikci]

this is also usefull when reviewing specific commit in pull request

github also not redirecting to branch

so if you do not want to change branch link behaviour, do you have any suggestion ? like should we check if branch deleted ?

[lunny]

I mean if there are serveal commits on a pull request and when view files on one commit mode. The link should be that commit's id but not end commit id?

[metiftikci]

This is how it works after change:

Show All Commit: last commit

View Range: last selected commit

View One Commit: selected commit