[PATCH] fast-import: always save out branches, tags and marks on checkpoint

[PATCH] fast-import: always save out branches, tags and marks on checkpoint

[Dmitry Ivankov]

checkpoint command causes fast-import to finish the current pack and
start a new one. If there are no (newly imported) objects in the pack
fast-import does nothing with the pack AND doesn't save out branches,
tags and marks.

Fix it by always saving out branches, tags and marks on a checkpoint.

Simple test case where no new objects are created is
$ fast-export $somebranch | sed $somebranch to $newbranch | fast-import
While it's running send checkpoint signals to fast-import to avoid
parsing the import stream. Non-fast-forward updates may happen if there
are merges in $somebranch history. The fast-import may fail on
checkpoints now. Not a regression as it'd fail the same way before if
import is to a new/empty repository - the intermediate packs won't be
empty and so a real checkpoint happens anyway.

Whether fast-export really should reuse $somebranch name for all commits
in it's history graph and so cause intermediate non-fast-forwads is a
separate topic to be discussed.

Signed-off-by: Dmitry Ivankov <divanorama@gmail.com>
---
 fast-import.c          |  9 ++++-----
 t/t9300-fast-import.sh | 26 ++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/fast-import.c b/fast-import.c
index f4d9969..4a3b93f 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -3101,12 +3101,11 @@ static void parse_ls(struct branch *b)
 static void checkpoint(void)
 {
 	checkpoint_requested = 0;
-	if (object_count) {
+	if (object_count)
 		cycle_packfile();
-		dump_branches();
-		dump_tags();
-		dump_marks();
-	}
+	dump_branches();
+	dump_tags();
+	dump_marks();
 }
 
 static void parse_checkpoint(void)
diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index 88fc407..03bfdef 100755
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -693,6 +693,32 @@ test_expect_success \
 	'git cat-file commit other >actual &&
 	test_cmp expect actual'
 
+cat >input2 <<INPUT_END
+reset refs/heads/branch2
+from refs/heads/other
+
+reset refs/heads/branch2
+from refs/heads/branch
+INPUT_END
+
+cat >input3 <<INPUT_END
+reset refs/heads/branch3
+from refs/heads/other
+
+checkpoint
+
+reset refs/heads/branch3
+from refs/heads/branch
+INPUT_END
+
+test_expect_success \
+	'F: intermediate non-fast-forward' \
+	'git fast-import <input2'
+
+test_expect_success \
+	'F: intermediate non-fast-forward with zero objects checkpoint should fail' \
+	'test_must_fail git fast-import <input3'
+
 ###
 ### series G
 ###
-- 
1.8.1.5