--- a/mercurial/cmdutil.py	Mon Jul 28 19:48:59 2014 -0400
+++ b/mercurial/cmdutil.py	Tue Jul 22 22:40:16 2014 -0700
@@ -1570,8 +1570,14 @@
     if not slowpath:
         for f in match.files():
             if follow and f not in pctx:
-                raise util.Abort(_('cannot follow file not in parent '
-                                   'revision: "%s"') % f)
+                # If the file exists, it may be a directory, so let it
+                # take the slow path.
+                if os.path.exists(repo.wjoin(f)):
+                    slowpath = True
+                    continue
+                else:
+                    raise util.Abort(_('cannot follow file not in parent '
+                                       'revision: "%s"') % f)
             filelog = repo.file(f)
             if not filelog:
                 # A zero count may be a directory or deleted file, so
@@ -1595,9 +1601,6 @@
     if slowpath:
         # See walkchangerevs() slow path.
         #
-        if follow:
-            raise util.Abort(_('can only follow copies/renames for explicit '
-                               'filenames'))
         # pats/include/exclude cannot be represented as separate
         # revset expressions as their filtering logic applies at file
         # level. For instance "-I a -X a" matches a revision touching
@@ -1629,7 +1632,10 @@
 
     filematcher = None
     if opts.get('patch') or opts.get('stat'):
-        if follow and not match.always():
+        # When following files, track renames via a special matcher.
+        # If we're forced to take the slowpath it means we're following
+        # at least one pattern/directory, so don't bother with rename tracking.
+        if follow and not match.always() and not slowpath:
             # _makelogfilematcher expects its files argument to be relative to
             # the repo root, so use match.files(), not pats.
             filematcher = _makelogfilematcher(repo, match.files(), followfirst)

--- a/tests/test-glog.t	Mon Jul 28 19:48:59 2014 -0400
+++ b/tests/test-glog.t	Tue Jul 22 22:40:16 2014 -0700
@@ -1645,13 +1645,28 @@
         ('symbol', 'filelog')
         ('string', 'aa'))))
 
-Test --follow on a directory
+Test --follow on a non-existent directory
 
   $ testlog -f dir
   abort: cannot follow file not in parent revision: "dir"
   abort: cannot follow file not in parent revision: "dir"
   abort: cannot follow file not in parent revision: "dir"
 
+Test --follow on a directory
+
+  $ hg up -q '.^'
+  $ testlog -f dir
+  []
+  (group
+    (func
+      ('symbol', '_matchfiles')
+      (list
+        (list
+          ('string', 'r:')
+          ('string', 'd:relpath'))
+        ('string', 'p:dir'))))
+  $ hg up -q tip
+
 Test --follow on file not in parent revision
 
   $ testlog -f a
@@ -1662,9 +1677,15 @@
 Test --follow and patterns
 
   $ testlog -f 'glob:*'
-  abort: can only follow copies/renames for explicit filenames
-  abort: can only follow copies/renames for explicit filenames
-  abort: can only follow copies/renames for explicit filenames
+  []
+  (group
+    (func
+      ('symbol', '_matchfiles')
+      (list
+        (list
+          ('string', 'r:')
+          ('string', 'd:relpath'))
+        ('string', 'p:glob:*'))))
 
 Test --follow on a single rename
 
@@ -1829,9 +1850,15 @@
           ('string', 'd:relpath'))
         ('string', 'p:a'))))
   $ testlog --removed --follow a
-  abort: can only follow copies/renames for explicit filenames
-  abort: can only follow copies/renames for explicit filenames
-  abort: can only follow copies/renames for explicit filenames
+  []
+  (group
+    (func
+      ('symbol', '_matchfiles')
+      (list
+        (list
+          ('string', 'r:')
+          ('string', 'd:relpath'))
+        ('string', 'p:a'))))
 
 Test --patch and --stat with --follow and --follow-first
 

--- a/tests/test-log.t	Mon Jul 28 19:48:59 2014 -0400
+++ b/tests/test-log.t	Tue Jul 22 22:40:16 2014 -0700
@@ -78,12 +78,52 @@
   summary:     c
   
 
--f, directory
+-f, non-existent directory
 
   $ hg log -f dir
   abort: cannot follow file not in parent revision: "dir"
   [255]
 
+-f, directory
+
+  $ hg up -q 3
+  $ hg log -f dir
+  changeset:   2:f8954cd4dc1f
+  user:        test
+  date:        Thu Jan 01 00:00:03 1970 +0000
+  summary:     c
+  
+-f, directory with --patch
+
+  $ hg log -f dir -p
+  changeset:   2:f8954cd4dc1f
+  user:        test
+  date:        Thu Jan 01 00:00:03 1970 +0000
+  summary:     c
+  
+  diff -r d89b0a12d229 -r f8954cd4dc1f dir/b
+  --- /dev/null* (glob)
+  +++ b/dir/b* (glob)
+  @@ -0,0 +1,1 @@
+  +a
+  
+
+-f, pattern
+
+  $ hg log -f -I 'dir**' -p
+  changeset:   2:f8954cd4dc1f
+  user:        test
+  date:        Thu Jan 01 00:00:03 1970 +0000
+  summary:     c
+  
+  diff -r d89b0a12d229 -r f8954cd4dc1f dir/b
+  --- /dev/null* (glob)
+  +++ b/dir/b* (glob)
+  @@ -0,0 +1,1 @@
+  +a
+  
+  $ hg up -q 4
+
 -f, a wrong style
 
   $ hg log -f -l1 --style something