URLs for directory paths should use `/tree/` instead of `/blob/`

[rhysd]

Repro

Run:

git brws .

Expected results

It opens https://github.com/{owner}/{repo}/tree/{hash}

Actual results

It opened https://github.com/{owner}/{repo}/blob/{hash}

Additional info

URLs for subdirectories (e.g. git brws ./src) are redirected from /blob/ URL to /tree/ URL automatically. However, only a root directory (e.g. git brws .) does not redirect the URL hence 404 error caused on a browser. I think git-brws should not rely on the redirect.

[rhysd]

TODO: Check behavior of GitLab and Bitbucket