[PATCH 1 of 4 V2] revset: add helper function to get tree depth

[Alexander Plavin]

# HG changeset patch
# User Alexander Plavin <alexander at plav.in>
# Date 1376074378 -14400
#      Fri Aug 09 22:52:58 2013 +0400
# Node ID 10862e95f769e7555ee54c0647595d508d5672ef
# Parent  da2209742e39683a5a42672e69133b1a20898973
revset: add helper function to get tree depth

diff -r da2209742e39 -r 10862e95f769 mercurial/revset.py
--- a/mercurial/revset.py	Fri Jul 19 02:09:13 2013 +0400
+++ b/mercurial/revset.py	Fri Aug 09 22:52:58 2013 +0400
@@ -1972,5 +1972,11 @@
     output = '\n'.join(('  '*l + s) for l, s in lines)
     return output
 
+def depth(tree):
+    if isinstance(tree, tuple):
+        return max(map(depth, tree)) + 1
+    else:
+        return 0
+
 # tell hggettext to extract docstrings from these functions:
 i18nfunctions = symbols.values()