[PATCH v2] line-log: fix crash when --first-parent is used

[Tzvetan Mikov <tmikov@gmail.com>]

line-log tries to access all parents of a commit, but only the first
parent has been loaded if "--first-parent" is specified, resulting
in a crash.

Limit the number of parents to one if "--first-parent" is specified.

Reported-by: Eric N. Vander Weele <ericvw@gmail.com>
Signed-off-by: Tzvetan Mikov <tmikov@gmail.com>
---
 PATCH v2: Add a test case (thanks Michael J Gruber)

 line-log.c          | 3 +++
 t/t4211-line-log.sh | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/line-log.c b/line-log.c
index 1008e72..86e7274 100644
--- a/line-log.c
+++ b/line-log.c
@@ -1141,6 +1141,9 @@ static int process_ranges_merge_commit(struct rev_info *rev, struct commit *comm
 	int i;
 	int nparents = commit_list_count(commit->parents);
 
+	if (nparents > 1 && rev->first_parent_only)
+	    nparents = 1;
+
 	diffqueues = xmalloc(nparents * sizeof(*diffqueues));
 	cand = xmalloc(nparents * sizeof(*cand));
 	parents = xmalloc(nparents * sizeof(*parents));
diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh
index 7369d3c..0901b30 100755
--- a/t/t4211-line-log.sh
+++ b/t/t4211-line-log.sh
@@ -94,4 +94,9 @@ test_expect_success '-L ,Y (Y == nlines + 2)' '
 	test_must_fail git log -L ,$n:b.c
 '
 
+test_expect_success '-L with --first-parent and a merge' '
+	git checkout parallel-change &&
+	git log --first-parent -L 1,1:b.c
+'
+
 test_done
-- 
1.9.1