[PATCH 3/5] range-set: satisfy non-empty ranges invariant

[Eric Sunshine <sunshine@sunshineco.com>]

range-set invariants are: ranges must be (1) non-empty, (2) disjoint,
(3) sorted in ascending order.

During processing, various range-set utility functions break the
invariants (for instance, by adding empty ranges), with the
expectation that a finalizing sort_and_merge_range_set() will restore
sanity.

sort_and_merge_range_set(), however, neglects to fold out empty
ranges, thus it fails to satisfy the non-empty constraint. Subsequent
range-set functions crash or throw an assertion failure upon
encountering such an anomaly. Rectify the situation by having
sort_and_merge_range_set() fold out empty ranges.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
---
 line-log.c          | 2 ++
 t/t4211-line-log.sh | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/line-log.c b/line-log.c
index 5234879..6f94d56 100644
--- a/line-log.c
+++ b/line-log.c
@@ -115,6 +115,8 @@ static void sort_and_merge_range_set(struct range_set *rs)
 	qsort(rs->ranges, rs->nr, sizeof(struct range), range_cmp);
 
 	for (i = 0; i < rs->nr; i++) {
+		if (rs->ranges[i].start == rs->ranges[i].end)
+			continue;
 		if (o > 0 && rs->ranges[i].start <= rs->ranges[o-1].end) {
 			if (rs->ranges[o-1].end < rs->ranges[i].end)
 				rs->ranges[o-1].end = rs->ranges[i].end;
diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh
index 1db1edd..12814c0 100755
--- a/t/t4211-line-log.sh
+++ b/t/t4211-line-log.sh
@@ -67,7 +67,7 @@ test_bad_opts "-L :foo:b.c" "no match"
 # There is a separate bug when an empty -L range is the first -L encountered,
 # thus to demonstrate this particular bug, the empty -L range must follow a
 # non-empty -L range.
-test_expect_failure '-L {empty-range} (any -L)' '
+test_expect_success '-L {empty-range} (any -L)' '
 	n=$(expr $(cat b.c | wc -l) + 1) &&
 	git log -L1,1:b.c -L$n:b.c
 '
-- 
1.8.3.4.1120.gc240c48