[PATCH v3 4/4] fast-export: make sure refs are updated properly

[Felipe Contreras <felipe.contreras@gmail.com>]

When an object has already been exported (and thus is in the marks) it
is flagged as SHOWN, so it will not be exported again, even if this time
it's exported through a different ref.

We don't need the object to be exported again, but we want the ref
updated, which doesn't happen.

Since we can't know if a ref was exported or not, let's just assume that
if the commit was marked (flags & SHOWN), the user still wants the ref
updated.

So:

 % git branch test master
 % git fast-export $mark_flags master
 % git fast-export $mark_flags test

Would export 'test' properly.

Additionally, this fixes issues with remote helpers; now they can push
refs wich objects have already been exported.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
---
 builtin/fast-export.c     | 11 ++++++++---
 t/t5800-remote-helpers.sh | 11 +++++++++++
 t/t9350-fast-export.sh    | 14 ++++++++++++++
 3 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 7fb6fe1..663a93d 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -523,11 +523,16 @@ static void get_tags_and_duplicates(struct object_array *pending,
 				typename(e->item->type));
 			continue;
 		}
-		if (commit->util) {
-			/* more than one name for the same object */
+
+		/*
+		 * This ref will not be updated through a commit, lets make
+		 * sure it gets properly upddated eventually.
+		 */
+		if (commit->util || commit->object.flags & SHOWN) {
 			if (!(commit->object.flags & UNINTERESTING))
 				string_list_append(extra_refs, full_name)->util = commit;
-		} else
+		}
+		if (!commit->util)
 			commit->util = full_name;
 	}
 }
diff --git a/t/t5800-remote-helpers.sh b/t/t5800-remote-helpers.sh
index e7dc668..69a145a 100755
--- a/t/t5800-remote-helpers.sh
+++ b/t/t5800-remote-helpers.sh
@@ -145,4 +145,15 @@ test_expect_failure 'push new branch with old:new refspec' '
 	compare_refs clone HEAD server refs/heads/new-refspec
 '
 
+test_expect_success 'push ref with existing object' '
+	(cd localclone &&
+	git branch point-to-master master &&
+	git push origin point-to-master
+	) &&
+
+	(cd server &&
+	git show-ref refs/heads/point-to-master
+	)
+'
+
 test_done
diff --git a/t/t9350-fast-export.sh b/t/t9350-fast-export.sh
index 6ea8f6f..a4178e3 100755
--- a/t/t9350-fast-export.sh
+++ b/t/t9350-fast-export.sh
@@ -446,4 +446,18 @@ test_expect_success 'proper extra refs handling' '
 	test_cmp expected actual
 '
 
+cat > expected << EOF
+reset refs/heads/master
+from :13
+
+EOF
+
+test_expect_success 'refs are updated even if no commits need to be exported' '
+	git fast-export --import-marks=tmp-marks \
+		--export-marks=tmp-marks master > /dev/null &&
+	git fast-export --import-marks=tmp-marks \
+		--export-marks=tmp-marks master > actual &&
+	test_cmp expected actual
+'
+
 test_done
-- 
1.8.0