tags-cache: directly perform a monimal walk for hgtagsfnodescache warming

We do something narrower than the path retrieving data. So lets use dedicated
code instead.

This provides further useful speedup:

### data-env-vars.name            = mozilla-try-2023-03-22-zstd-sparse-revlog
  # benchmark.name                = hg.debug.debug-update-cache
  # bin-env-vars.hg.flavor        = default
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.pre-state  = warm
before-this-series:  19.947581
skip-fnode-filter:   18.916804   (-5.17%, -1.03)
use-rev-num:         17.493725  (-12.30%, -2.45)
this-changesets:     15.919466  (-20.19%, -4.03)

mercurial/tags.py

@@ -21,6 +21,7 b' from .node import ('
     short,
 )
 from .i18n import _
+from .revlogutils.constants import ENTRY_NODE_ID
 from . import (
     encoding,
     error,
@@ -30,6 +31,7 b' from . import ('
 )
 from .utils import stringutil
 
+
 # Tags computation can be expensive and caches exist to make it fast in
 # the common case.
 #
@@ -83,7 +85,29 b' from .utils import stringutil'
 def warm_cache(repo):
     """ensure the cache is properly filled"""
     unfi = repo.unfiltered()
-    _getfnodes(repo.ui, repo, revs=unfi.changelog.revs())
+    fnodescache = hgtagsfnodescache(unfi)
+    validated_fnodes = set()
+    unknown_entries = set()
+    flog = None
+
+    entries = enumerate(repo.changelog.index)
+    node_revs = ((e[ENTRY_NODE_ID], rev) for (rev, e) in entries)
+
+    for node, rev in node_revs:
+        fnode = fnodescache.getfnode(node=node, rev=rev)
+        if fnode != repo.nullid:
+            if fnode not in validated_fnodes:
+                if flog is None:
+                    flog = repo.file(b'.hgtags')
+                if flog.hasnode(fnode):
+                    validated_fnodes.add(fnode)
+                else:
+                    unknown_entries.add(node)
+
+    if unknown_entries:
+        fnodescache.refresh_invalid_nodes(unknown_entries)
+
+    fnodescache.write()
 
 
 def fnoderevs(ui, repo, revs):