project: stop symlinking svn under .git/

This path only matters to users of `git svn` who manually run it in
local projects after they get a full repo client checkout.  With svn
usage falling in general, and with the fact that the source checkout
now symlinks its .git/ state to the internal projects/ path, we don't
need to manage this anymore.

It means the path won't be shared among multiple local projects that
have the same remote, but so it goes.  It was an optimization only,
not functionality required for correctness.  We want to simplify the
internals to stop messing with git state, and this particular path
doesn't seem worth the effort to maintain.

We don't undo any existing svn symlinks if they exist since repo does
not care about them, and their existence doesn't hurt anything.

Bug: https://crbug.com/gerrit/15460
Change-Id: Ie8496b275bcc589771aa9f4ee874ed2ee6d5241d
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/327517
Reviewed-by: Jonathan Nieder <jrn@google.com>
Tested-by: Mike Frysinger <vapier@google.com>
diff --git a/project.py b/project.py
index a2b98d8..db44cde 100644
--- a/project.py
+++ b/project.py
@@ -458,7 +458,7 @@
 class Project(object):
   # These objects can be shared between several working trees.
   shareable_files = ['description', 'info']
-  shareable_dirs = ['hooks', 'objects', 'rr-cache', 'svn']
+  shareable_dirs = ['hooks', 'objects', 'rr-cache']
 
   def __init__(self,
                manifest,