diff mercurial/patch.py @ 16124:0e0060bf2f44 stable

patch: fuzz more aggressively to match patch(1) behaviour

The previous code was assuming a default context of 3 lines. When fuzzing, it
would take this value in account to reduce the amount of removed line from
hunks top or bottom. For instance, if a hunk has only 2 lines of bottom
context, fuzzing with fuzz=1 would do nothing and with fuzz=2 it would remove
one of those lines. A hunk with one line of bottom context could not be fuzzed
at all.  patch(1) has apparently no such restrictions and takes the fuzz level
at face value.

- test-import.t: fuzz/offset changes at the beginning of file are explained by
  the new fuzzing behaviour and match patch(1) ones. Patching locations are
  different but those of my patch(1) do not make a lot of sense right now
  (patched output are the same)

- test-import-bypass.t: more agressive fuzzing makes a patching supposed to
  fail because of context, succeed. Change the diff to avoid this.

- test-mq-merge.t: more agressive fuzzing would allow the merged patch to apply
  with fuzz, but fortunately we disallow this behaviour. The new output is
  kept.

I have not enough experience with patch(1) fuzzing to know whether aligning our
implementation on it is a good or bad idea. Until now, it has been the
implementation reference. For instance, "qpush" tolerates fuzz (test-mq-merge.t
runs the special case of pushing merge revisions where fuzzing is forbidden).

--- a/mercurial/patch.py	Mon Feb 13 16:47:31 2012 +0100
+++ b/mercurial/patch.py	Mon Feb 13 17:22:35 2012 +0100
@@ -973,7 +973,7 @@
         # this removes context lines from the top and bottom of list 'l'.  It
         # checks the hunk to make sure only context lines are removed, and then
         # returns a new shortened list of lines.
-        fuzz = min(fuzz, len(old)-1)
+        fuzz = min(fuzz, len(old))
         if fuzz:
             top = 0
             bot = 0
@@ -991,18 +991,8 @@
                     else:
                         break
 
-            # top and bot now count context in the hunk
-            # adjust them if either one is short
-            context = max(top, bot, 3)
-            if bot < context:
-                bot = max(0, fuzz - (context - bot))
-            else:
-                bot = min(fuzz, bot)
-            if top < context:
-                top = max(0, fuzz - (context - top))
-            else:
-                top = min(fuzz, top)
-
+            bot = min(fuzz, bot)
+            top = min(fuzz, top)
             return old[top:len(old)-bot], new[top:len(new)-bot], top
         return old, new, 0