bdiff: give slight preference to removing trailing lines
authorMads Kiilerich <madski@unity3d.com>
Tue, 15 Nov 2016 21:56:49 +0100
changeset 30442 96f2f50d923f
parent 30441 3633403888ae
child 30443 2e484bdea8c4
bdiff: give slight preference to removing trailing lines [This change could be folded into the previous changeset to minimize the repo churn ...] Similar to the previous change, introduce an exception to the general preference for matches in the middle of bdiff ranges: If the best match on the B side starts at the beginning of the bdiff range, don't aim for the middle-most A side match but for the earliest. New (later) matches on the A side will only be considered better if the corresponding match on the B side *not* is at the beginning of the range. Thus, if the best (middle-most) match on the B side turns out to be at the beginning of the range, the earliest match on the A side will be used. The bundle size for 4.0 (hg bundle --base null -r 4.0 x.hg) happens to go from 22807275 to 22808120 bytes - a 0.004% increase.
mercurial/bdiff.c
tests/test-bdiff.py
tests/test-bdiff.py.out
--- a/mercurial/bdiff.c	Tue Nov 15 21:56:49 2016 +0100
+++ b/mercurial/bdiff.c	Tue Nov 15 21:56:49 2016 +0100
@@ -184,7 +184,7 @@
 				mj = j;
 				mk = k;
 			} else if (k == mk) {
-				if (i > mi && i <= half) {
+				if (i > mi && i <= half && j > b1) {
 					/* same match but closer to half */
 					mi = i;
 					mj = j;
--- a/tests/test-bdiff.py	Tue Nov 15 21:56:49 2016 +0100
+++ b/tests/test-bdiff.py	Tue Nov 15 21:56:49 2016 +0100
@@ -88,7 +88,7 @@
 showdiff('a\n', 'a\n' * 3)
 print("Diff 1 to 5 lines - preference for appending:")
 showdiff('a\n', 'a\n' * 5)
-print("Diff 3 to 1 lines - preference for balanced recursion:")
+print("Diff 3 to 1 lines - preference for removing trailing lines:")
 showdiff('a\n' * 3, 'a\n')
-print("Diff 5 to 1 lines - preference for balanced recursion:")
+print("Diff 5 to 1 lines - preference for removing trailing lines:")
 showdiff('a\n' * 5, 'a\n')
--- a/tests/test-bdiff.py.out	Tue Nov 15 21:56:49 2016 +0100
+++ b/tests/test-bdiff.py.out	Tue Nov 15 21:56:49 2016 +0100
@@ -68,17 +68,15 @@
   'a\na\na\na\na\n'):
  'a\n'
  2 2 '' -> 'a\na\na\na\n'
-Diff 3 to 1 lines - preference for balanced recursion:
+Diff 3 to 1 lines - preference for removing trailing lines:
 showdiff(
   'a\na\na\n',
   'a\n'):
- 0 2 'a\n' -> ''
  'a\n'
- 4 6 'a\n' -> ''
-Diff 5 to 1 lines - preference for balanced recursion:
+ 2 6 'a\na\n' -> ''
+Diff 5 to 1 lines - preference for removing trailing lines:
 showdiff(
   'a\na\na\na\na\n',
   'a\n'):
- 0 4 'a\na\n' -> ''
  'a\n'
- 6 10 'a\na\n' -> ''
+ 2 10 'a\na\na\na\n' -> ''