tags: take lock instead of wlock before writing hgtagsfnodes1 cache

This cache is shared across stores and hence we should take store lock before
writing to it. Otherwise there will be race where one share with wlock is
writing to this cache and other share with wlock is trying to read it
simultaneously.

Differential Revision: https://phab.mercurial-scm.org/D9001

mercurial/tags.py

@@ -838,7 +838,7 b' class hgtagsfnodescache(object):'
         repo = self._repo
 
         try:
-            lock = repo.wlock(wait=False)
+            lock = repo.lock(wait=False)
         except error.LockError:
             repo.ui.log(
                 b'tagscache',

tests/test-tags.t

@@ -156,7 +156,7 b' Tag cache debug info written to blackbox'
 Failure to acquire lock results in no write
 
   $ rm -f .hg/cache/tags2-visible .hg/cache/hgtagsfnodes1
-  $ echo 'foo:1' > .hg/wlock
+  $ echo 'foo:1' > .hg/store/lock
   $ hg identify
   b9154636be93 tip
   $ hg blackbox -l 6
@@ -170,7 +170,7 b' Failure to acquire lock results in no wr'
   $ fnodescacheexists
   no fnodes cache
 
-  $ rm .hg/wlock
+  $ rm .hg/store/lock
 
   $ rm -f .hg/cache/tags2-visible .hg/cache/hgtagsfnodes1
   $ hg identify