manifestcache: protect write with `wlock` instead of `lock`

The `wlock` is taken by both `update` and `commit` type operation. This would
help persisting the cache more aggressively.

An explicit test is introduced. However, we can already see the effect of this
change on earlier test output.

mercurial/debugcommands.py

@@ -1476,13 +1476,13 b' def debugmanifestfulltextcache(ui, repo,'
             raise error.Abort(msg)
 
     if opts.get(r'clear'):
-        with repo.lock():
+        with repo.wlock():
             cache = getcache()
             cache.clear(clear_persisted_data=True)
             return
 
     if add:
-        with repo.lock():
+        with repo.wlock():
             m = repo.manifestlog
             store = m.getstorage(b'')
             for n in add:

mercurial/manifest.py

@@ -1435,11 +1435,11 b' class manifestrevlog(object):'
 
     def _setupmanifestcachehooks(self, repo):
         """Persist the manifestfulltextcache on lock release"""
-        if not util.safehasattr(repo, '_lockref'):
+        if not util.safehasattr(repo, '_wlockref'):
             return
 
         self._fulltextcache._opener = repo.cachevfs
-        if repo._currentlock(repo._lockref) is None:
+        if repo._currentlock(repo._wlockref) is None:
             return
 
         reporef = weakref.ref(repo)

tests/test-clone.t

@@ -58,6 +58,7 b' Ensure branchcache got copied over:'
 
   $ ls .hg/cache
   branch2-served
+  manifestfulltextcache
   rbc-names-v1
   rbc-revs-v1
 

tests/test-hardlinks.t

@@ -290,7 +290,7 b' Update back to revision 12 in r4 should '
   1 r4/.hg/branch
   2 r4/.hg/cache/branch2-base
   2 r4/.hg/cache/branch2-served
-  2 r4/.hg/cache/manifestfulltextcache (reporevlogstore !)
+  1 r4/.hg/cache/manifestfulltextcache (reporevlogstore !)
   2 r4/.hg/cache/rbc-names-v1
   2 r4/.hg/cache/rbc-revs-v1
   1 r4/.hg/dirstate

tests/test-manifest.t

@@ -106,7 +106,9 b' Reminder of the manifest log content'
 Showing the content of the caches after the above operations
 
   $ hg debugmanifestfulltextcache
-  cache empty
+  cache contains 1 manifest entries, in order of most to least recent:
+  id: 1e01206b1d2f72bd55f2a33fa8ccad74144825b7, size 133 bytes
+  total cache data size 157 bytes, on-disk 157 bytes
 
 (Clearing the cache in case of any content)
 
@@ -183,3 +185,19 b' Commit should have the new node cached:'
   $ hg log -r 'ancestors(., 1)' --debug | grep 'manifest:'
   manifest:    1:1e01206b1d2f72bd55f2a33fa8ccad74144825b7
   manifest:    2:26b8653b67af8c1a0a0317c4ee8dac50a41fdb65
+
+hg update should warm the cache too
+
+(force dirstate check to avoid flackiness in manifest order)
+  $ hg debugrebuilddirstate
+
+  $ hg update 0
+  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  $ hg debugmanifestfulltextcache
+  cache contains 3 manifest entries, in order of most to least recent:
+  id: fce2a30dedad1eef4da95ca1dc0004157aa527cf, size 87 bytes
+  id: 26b8653b67af8c1a0a0317c4ee8dac50a41fdb65, size 133 bytes
+  id: 1e01206b1d2f72bd55f2a33fa8ccad74144825b7, size 133 bytes
+  total cache data size 425 bytes, on-disk 425 bytes
+  $ hg log -r '0' --debug | grep 'manifest:'
+  manifest:    0:fce2a30dedad1eef4da95ca1dc0004157aa527cf