blame: add a test to cover blame_coalesce()

Signed-off-by: Barret Rhoden <brho@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t8003-blame-corner-cases.sh

@@ -275,4 +275,40 @@ test_expect_success 'blame file with CRLF core.autocrlf=true' '
 	grep "A U Thor" actual
 '
 
+# Tests the splitting and merging of blame entries in blame_coalesce().
+# The output of blame is the same, regardless of whether blame_coalesce() runs
+# or not, so we'd likely only notice a problem if blame crashes or assigned
+# blame to the "splitting" commit ('SPLIT' below).
+test_expect_success 'blame coalesce' '
+	cat >giraffe <<-\EOF &&
+	ABC
+	DEF
+	EOF
+	git add giraffe &&
+	git commit -m "original file" &&
+	oid=$(git rev-parse HEAD) &&
+
+	cat >giraffe <<-\EOF &&
+	ABC
+	SPLIT
+	DEF
+	EOF
+	git add giraffe &&
+	git commit -m "interior SPLIT line" &&
+
+	cat >giraffe <<-\EOF &&
+	ABC
+	DEF
+	EOF
+	git add giraffe &&
+	git commit -m "same contents as original" &&
+
+	cat >expect <<-EOF &&
+	$oid 1) ABC
+	$oid 2) DEF
+	EOF
+	git -c core.abbrev=40 blame -s giraffe >actual &&
+	test_cmp expect actual
+'
+
 test_done