[PATCH 1 of 6 V3] revset: add helper function to get revset parse 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 f32bf1774cc3e6cd7ee99a7be2724daa23223a98
# Parent  04c91751cbf8abc1f3ea56c67ca4988e0e8e61a5
revset: add helper function to get revset parse tree depth

diff -r 04c91751cbf8 -r f32bf1774cc3 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()