log: restore cache used by --copies

The {filelog -> linkrev -> copyfrom} cache was refactored and broken by:

  changeset:   10060:f780b1098efc
  user:        Patrick Mezard <[e-mail]>
  date:        Sun Dec 13 18:06:24 2009 +0100
  summary:     templatekw: change {file_copies} behaviour, add
               {file_copies_switch}

With --copies, this cache is accessed for every touched file of every revision.
Unfortunately it is recreated for every revision, which means filelogs are
parsed again. This patch makes the cache global again for all revisions.

A couple of indicative timings of "hg log --copies", before and after:

hg:                       44s /     5s
mozilla --limit 10000:  3m51s /  2m32s
mozilla:               23m46s / 12m23s

I do not know any good tool to trace memory consumption of these runs for
comparisons. Watching the full mozilla run in top, the process did not seem to
misbehave.

mercurial/commands.py

@@ -3849,9 +3849,11 b' def log(ui, repo, *pats, **opts):'
     limit = cmdutil.loglimit(opts)
     count = 0
 
-    endrev = None
-    if opts.get('copies') and opts.get('rev'):
+    getrenamed, endrev = None, None
+    if opts.get('copies'):
+        if opts.get('rev'):
         endrev = max(scmutil.revrange(repo, opts.get('rev'))) + 1
+        getrenamed = templatekw.getrenamedfn(repo, endrev=endrev)
 
     df = False
     if opts["date"]:
@@ -3895,9 +3897,8 b' def log(ui, repo, *pats, **opts):'
                 return
 
         copies = None
-        if opts.get('copies') and rev:
+        if getrenamed is not None and rev:
             copies = []
-            getrenamed = templatekw.getrenamedfn(repo, endrev=endrev)
             for fn in ctx.files():
                 rename = getrenamed(fn, rev)
                 if rename: