share: don't recreate the source repo each time

Previously, every time you asked for the source repo of a shared working copy it
would recreate the repo object, which required calling reposetup. With certain
extension enabled, this can be quite expensive, and it can happen many times
(for instance, share attaches a post transaction hook to update bookmarks that
triggers this).

The fix is to just cache the repo object instead of constantly recreating it.

hgext/share.py

@@ -157,10 +157,15 b' def _getsrcrepo(repo):'
     if repo.sharedpath == repo.path:
         return None
 
+    if util.safehasattr(repo, 'srcrepo') and repo.srcrepo:
+        return repo.srcrepo
+
     # the sharedpath always ends in the .hg; we want the path to the repo
     source = repo.vfs.split(repo.sharedpath)[0]
     srcurl, branches = parseurl(source)
-    return repository(repo.ui, srcurl)
+    srcrepo = repository(repo.ui, srcurl)
+    repo.srcrepo = srcrepo
+    return srcrepo
 
 def getbkfile(orig, repo):
     if _hassharedbookmarks(repo):