# HG changeset patch
# User Boris Feld <boris.feld@octobus.net>
# Date 1534279453 25200
# Node ID 152ae0f84f9ab78b2c5efab83a84458215e2407d
# Parent  8f83a953dddf6bacba069a95221f9285ba9bdb28
revlog: split and document good delta conditional

The logic is still identical, but having each conditional on its own helps to
document them and will help to edit them in the future.

diff -r 8f83a953dddf -r 152ae0f84f9a mercurial/revlog.py
--- a/mercurial/revlog.py	Fri Jul 27 19:09:41 2018 +0200
+++ b/mercurial/revlog.py	Tue Aug 14 13:44:13 2018 -0700
@@ -2473,9 +2473,30 @@
             # certain size. Be also apply this tradeoff here and relax span
             # constraint for small enought content.
             maxdist = self._srmingapsize
-        if (distance > maxdist or deltainfo.deltalen > textlen or
-            deltainfo.compresseddeltalen > textlen * 2 or
-            (self._maxchainlen and deltainfo.chainlen > self._maxchainlen)):
+
+        # Bad delta from read span:
+        #
+        #   If the span of data read is larger than the maximum allowed.
+        if maxdist < distance:
+            return False
+
+        # Bad delta from new delta size:
+        #
+        #   If the delta size is larger than the target text, storing the
+        #   delta will be inefficient.
+        if textlen < deltainfo.deltalen:
+            return False
+
+        # Bad delta from cumulated payload size:
+        #
+        #   If the sum of delta get larger than K * target text length.
+        if textlen * 2  < deltainfo.compresseddeltalen:
+            return False
+
+        # Bad delta from chain length:
+        #
+        #   If the number of delta in the chain gets too high.
+        if self._maxchainlen and  self._maxchainlen < deltainfo.chainlen:
             return False
 
         return True