remotefilelog: avoid accessing repo instance after dispatch

Upstream commit c5e6c1ba1c79 (hg: don't reuse repo instance after
unshare(), 2018-09-12) poisoned the repo instance after
unshare(). That made `hg unshare` fail with remotefilelog because we
tried to close the fileserverclient after dispatch by accessing it via
the repo. This patch fixes that by storing the reference to the
fileserverclient at the beginning of dispatch.

An analogous patch was sent for remotefilelog version in FB's
hg-experimental as D5246.

Differential Revision: https://phab.mercurial-scm.org/D5253

hgext/remotefilelog/__init__.py

@@ -542,14 +542,17 b' def onetimeclientsetup(ui):'
 
     # close cache miss server connection after the command has finished
     def runcommand(orig, lui, repo, *args, **kwargs):
-        try:
-            return orig(lui, repo, *args, **kwargs)
-        finally:
+        fileservice = None
             # repo can be None when running in chg:
             # - at startup, reposetup was called because serve is not norepo
             # - a norepo command like "help" is called
             if repo and isenabled(repo):
-                repo.fileservice.close()
+            fileservice = repo.fileservice
+        try:
+            return orig(lui, repo, *args, **kwargs)
+        finally:
+            if fileservice:
+                fileservice.close()
     extensions.wrapfunction(dispatch, 'runcommand', runcommand)
 
     # disappointing hacks below

tests/test-remotefilelog-share.t

@@ -22,3 +22,4 b''
   $ hg share source dest
   updating working directory
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg -R dest unshare