The command arc browse FILE now support Subversion repositories.

It's not very clear if this ever worked for a period before 2020:

https://we.phorge.it/source/arcanist/browse/master/src/ref/ArcanistRepositoryRef.php;80f5166b701d788fb598c98d60fd707ea85fff6b$126-127

Anyway, now it works.

Closes T15541

In a random Phorge, create a new Subversion repository in Diffusion
with some contents, like these:

README.md
trunk/lol.txt

Then clone that repository with your usual URL, that is:

svn checkout svn+ssh://phab@phorge.localhost/source/example-svn-repository example-svn-repository

All of these work:

• arc browse README.md
• arc browse trunk/lol.txt
• cd trunk; arc browse lol.txt; cd -

In the very same repository, manually go to the Diffusion > Subversion menu and set "trunk/"
as sub-directory - so the web interface only shows the trunk directory.

All of these still work:

• arc browse trunk/lol.txt
• cd trunk; arc browse lo.txt; cd -

Inside the directory of arcanist, all of these work as expected, opening the browser
web on the specified file and on the specified branch:

• arc browse README.md
• arc browse README.md --branch stable
• arc browse README.md --branch master
• cd bin; arc browse arc; cd -
• arc browse bin/arc

The browser web carefully opens as expected.
If it worked before, it works now, but also on Subversion repos.