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>

diff --git a/builtin/clone.c b/builtin/clone.c
index 00535d0178f1a0ee562bf008e8b072f68410dc3d..8539b8de64076dae79f993552828b65440e6c357 100644 (file)
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -491,16 +491,26 @@ static void write_remote_refs(const struct ref *local_refs)
 {
        const struct ref *r;
 
-       lock_packed_refs(LOCK_DIE_ON_ERROR);
+       struct ref_transaction *t;
+       struct strbuf err = STRBUF_INIT;
+
+       t = ref_transaction_begin(&err);
+       if (!t)
+               die("%s", err.buf);
 
        for (r = local_refs; r; r = r->next) {
                if (!r->peer_ref)
                        continue;
-               add_packed_ref(r->peer_ref->name, r->old_sha1);
+               if (ref_transaction_create(t, r->peer_ref->name, r->old_sha1,
+                                          0, NULL, &err))
+                       die("%s", err.buf);
        }
 
-       if (commit_packed_refs())
-               die_errno("unable to overwrite old ref-pack file");
+       if (initial_ref_transaction_commit(t, &err))
+               die("%s", err.buf);
+
+       strbuf_release(&err);
+       ref_transaction_free(t);
 }
 
 static void write_followtags(const struct ref *refs, const char *msg)

diff --git a/refs.c b/refs.c
index 081ea6eada6b4193ac6e14c35054e5447471c0b0..c6f2f64bc51125c6680c8e871856bdd2b9b5a563 100644 (file)
--- 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;

diff --git a/refs.h b/refs.h
index 5f3bea7a42b474e7f6cfe1fa9dcdd2c184b3f722..9602889c3c0b8a7eb47661008769ead55687262f 100644 (file)
--- a/refs.h
+++ b/refs.h
@@ -365,6 +365,20 @@ int ref_transaction_verify(struct ref_transaction *transaction,
 int ref_transaction_commit(struct ref_transaction *transaction,
                           struct strbuf *err);
 
+/*
+ * Like ref_transaction_commit(), but optimized for creating
+ * references when originally initializing a repository (e.g., by "git
+ * clone"). It writes the new references directly to packed-refs
+ * without locking the individual references.
+ *
+ * It is a bug to call this function when there might be other
+ * processes accessing the repository or if there are existing
+ * references that might conflict with the ones being created. All
+ * old_sha1 values must either be absent or NULL_SHA1.
+ */
+int initial_ref_transaction_commit(struct ref_transaction *transaction,
+                                  struct strbuf *err);
+
 /*
  * Free an existing transaction and all associated data.
  */