[PATCH 2/2] diff: fix a double off-by-one with --ignore-space-at-eol

[Johannes Schindelin <johannes.schindelin@gmx.de>]

When comparing two lines, ignoring any whitespace at the end, we first
try to match as many bytes as possible and break out of the loop only
upon mismatch, to let the remainder be handled by the code shared with
the other whitespace-ignoring code paths.

When comparing the bytes, however, we incremented the counters always,
even if the bytes did not match. And because we fall through to  the
space-at-eol handling at that point, it is as if that mismatch never
happened.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 t/t4033-diff-patience.sh | 2 +-
 xdiff/xpatience.c        | 2 +-
 xdiff/xutils.c           | 6 ++++--
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/t/t4033-diff-patience.sh b/t/t4033-diff-patience.sh
index 5f0d0b1..113304d 100755
--- a/t/t4033-diff-patience.sh
+++ b/t/t4033-diff-patience.sh
@@ -5,7 +5,7 @@ test_description='patience diff algorithm'
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-diff-alternative.sh
 
-test_expect_failure '--ignore-space-at-eol with a single appended character' '
+test_expect_success '--ignore-space-at-eol with a single appended character' '
 	printf "a\nb\nc\n" >pre &&
 	printf "a\nbX\nc\n" >post &&
 	test_must_fail git diff --no-index \
diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
index 04e1a1a..a613efc 100644
--- a/xdiff/xpatience.c
+++ b/xdiff/xpatience.c
@@ -1,6 +1,6 @@
 /*
  *  LibXDiff by Davide Libenzi ( File Differential Library )
- *  Copyright (C) 2003-2009 Davide Libenzi, Johannes E. Schindelin
+ *  Copyright (C) 2003-2016 Davide Libenzi, Johannes E. Schindelin
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index 62cb23d..027192a 100644
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c
@@ -200,8 +200,10 @@ int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
 				return 0;
 		}
 	} else if (flags & XDF_IGNORE_WHITESPACE_AT_EOL) {
-		while (i1 < s1 && i2 < s2 && l1[i1++] == l2[i2++])
-			; /* keep going */
+		while (i1 < s1 && i2 < s2 && l1[i1] == l2[i2]) {
+			i1++;
+			i2++;
+		}
 	}
 
 	/*
-- 
2.9.0.278.g1caae67