octopus: reenable fast-forward merges

The fast-forward logic is never being triggered because $common and
$MRC are never equivalent. $common is initialized to a commit id by
merge-base and MRC is initialized to HEAD. Fix this by initializing
$MRC to the commit id for HEAD so that its possible for $MRC and
$common to be equal.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-merge-octopus.sh

@@ -44,7 +44,7 @@ esac
 # MRC is the current "merge reference commit"
 # MRT is the current "merge result tree"
 
-MRC=$head MSG= PARENT="-p $head"
+MRC=$(git rev-parse --verify -q $head) MSG= PARENT="-p $head"
 MRT=$(git write-tree)
 CNT=1 ;# counting our head
 NON_FF_MERGE=0

t/t7602-merge-octopus-many.sh

@@ -82,4 +82,22 @@ test_expect_success 'merge up-to-date output uses pretty names' '
 	git merge c4 c5 >actual &&
 	test_cmp actual expected
 '
+
+cat >expected <<\EOF
+Fast-forwarding to: c1
+Trying simple merge with c2
+Merge made by octopus.
+ c1.c |    1 +
+ c2.c |    1 +
+ 2 files changed, 2 insertions(+), 0 deletions(-)
+ create mode 100644 c1.c
+ create mode 100644 c2.c
+EOF
+
+test_expect_success 'merge fast-forward output uses pretty names' '
+	git reset --hard c0 &&
+	git merge c1 c2 >actual &&
+	test_cmp actual expected
+'
+
 test_done