t8003: check output of coalesced blame

Commit f0cbe742f4 (blame: add a test to cover blame_coalesce(),
2019-06-20) added a test case where blame can usefully coalesce two
groups of lines. But since it relies on the normal blame output, it only
exercises the code and can't tell whether the lines were actually
joined into a single group.

However, by using --porcelain output, we can see how git-blame considers
the groupings (and likewise how the coalescing might have a real
user-visible impact for a tool that uses the porcelain-output
groupings). This lets us confirm that we are indeed coalescing correctly
(and the fact that this test case requires coalescing can be verified by
dropping the call to blame_coalesce(), causing the test to fail).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t8003-blame-corner-cases.sh

@@ -274,10 +274,6 @@ 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
@@ -303,10 +299,11 @@ test_expect_success 'blame coalesce' '
 	git commit -m "same contents as original" &&
 
 	cat >expect <<-EOF &&
-	$oid 1) ABC
-	$oid 2) DEF
+	$oid 1 1 2
+	$oid 2 2
 	EOF
-	git -c core.abbrev=40 blame -s giraffe >actual &&
+	git blame --porcelain giraffe >actual.raw &&
+	grep "^$oid" actual.raw >actual &&
 	test_cmp expect actual
 '