initial_ref_transaction_commit(): function for initial ref creation

"git clone" uses shortcuts when creating the initial set of
references:

* It writes them directly to packed-refs.

* It doesn't lock the individual references (though it does lock the
  packed-refs file).

* It doesn't check for refname conflicts between two new references or
  between one new reference and any hypothetical old ones.

* It doesn't create reflog entries for the reference creations.

This functionality was implemented in builtin/clone.c. But really that
file shouldn't have such intimate knowledge of how references are
stored. So provide a new function in the refs API,
initial_ref_transaction_commit(), which can be used for initial
reference creation. The new function is based on the ref_transaction
interface.

This means that we can make some other functions private to the refs
module. That will be done in a followup commit.

It would seem to make sense to add a test here that there are no
existing references, because that is how the function *should* be
used. But in fact, the "testgit" remote helper appears to call it
*after* having set up refs/remotes/<name>/HEAD and
refs/remotes/<name>/master, so we can't be so strict. For now, the
function trusts its caller to only call it when it makes sense. Future
commits will add some more limited sanity checks.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/refs.c b/refs.c
index 081ea6eada..c6f2f64bc5 100644
--- a/refs.c
+++ b/refs.c
@@ -4076,6 +4076,53 @@ cleanup:
 	return ret;
 }
 
+int initial_ref_transaction_commit(struct ref_transaction *transaction,
+				   struct strbuf *err)
+{
+	int ret = 0, i;
+	int n = transaction->nr;
+	struct ref_update **updates = transaction->updates;
+
+	assert(err);
+
+	if (transaction->state != REF_TRANSACTION_OPEN)
+		die("BUG: commit called for transaction that is not open");
+
+	for (i = 0; i < n; i++) {
+		struct ref_update *update = updates[i];
+
+		if ((update->flags & REF_HAVE_OLD) &&
+		    !is_null_sha1(update->old_sha1))
+			die("BUG: initial ref transaction with old_sha1 set");
+	}
+
+	if (lock_packed_refs(0)) {
+		strbuf_addf(err, "unable to lock packed-refs file: %s",
+			    strerror(errno));
+		ret = TRANSACTION_GENERIC_ERROR;
+		goto cleanup;
+	}
+
+	for (i = 0; i < n; i++) {
+		struct ref_update *update = updates[i];
+
+		if ((update->flags & REF_HAVE_NEW) &&
+		    !is_null_sha1(update->new_sha1))
+			add_packed_ref(update->refname, update->new_sha1);
+	}
+
+	if (commit_packed_refs()) {
+		strbuf_addf(err, "unable to commit packed-refs file: %s",
+			    strerror(errno));
+		ret = TRANSACTION_GENERIC_ERROR;
+		goto cleanup;
+	}
+
+cleanup:
+	transaction->state = REF_TRANSACTION_CLOSED;
+	return ret;
+}
+
 char *shorten_unambiguous_ref(const char *refname, int strict)
 {
 	int i;