Add command "Copy link to the file" with specifying the current commit hash, not the branch name

[akudiyar]

Currently the links look like

https://github.com/xxx/yyy/blob/master/a/b/c/file.pyl#L374

But for using this somewhere in the bug trackers or documentation, it's more useful to have a link like

https://github.com/xxx/yyy/blob/abcd1234/a/b/c/file.pyl#L374

where abcd1234 -- the current commit hash.

In a constantly evolving project links to the master HEAD can quickly become pointing to a wrong location.