refs.c: change ref_transaction_create to do error checking and return status

Do basic error checking in ref_transaction_create() and make it return
non-zero on error. Update all callers to check the result of
ref_transaction_create(). There are currently no conditions in _create that
will return error but there will be in the future. Add an err argument that
will be updated on failure.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 3067b11310fb01e9e05a1988898566f211601e07..41121fa37bcb12a5fbd5180da6e0e3f316a4098e 100644 (file)
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -226,7 +226,9 @@ static const char *parse_cmd_create(struct strbuf *input, const char *next)
        if (*next != line_termination)
                die("create %s: extra input: %s", refname, next);
 
        if (*next != line_termination)
                die("create %s: extra input: %s", refname, next);
 

-       ref_transaction_create(transaction, refname, new_sha1, update_flags);
+       if (ref_transaction_create(transaction, refname, new_sha1,
+                                  update_flags, &err))
+               die("%s", err.buf);

 
        update_flags = 0;
        free(refname);
 
        update_flags = 0;
        free(refname);

diff --git a/refs.c b/refs.c
index 3f05e88329216ab4849b54df3c3e034dcf173ff3..c49f1c609ab7507ccc0fcc837c5b2b0fdf0071ee 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -3449,18 +3449,24 @@ int ref_transaction_update(struct ref_transaction *transaction,
        return 0;
 }
 
        return 0;
 }
 

-void ref_transaction_create(struct ref_transaction *transaction,
-                           const char *refname,
-                           const unsigned char *new_sha1,
-                           int flags)
+int ref_transaction_create(struct ref_transaction *transaction,
+                          const char *refname,
+                          const unsigned char *new_sha1,
+                          int flags,
+                          struct strbuf *err)

 {
 {

-       struct ref_update *update = add_update(transaction, refname);
+       struct ref_update *update;
+
+       if (!new_sha1 || is_null_sha1(new_sha1))
+               die("BUG: create ref with null new_sha1");
+
+       update = add_update(transaction, refname);

 
 

-       assert(!is_null_sha1(new_sha1));

        hashcpy(update->new_sha1, new_sha1);
        hashclr(update->old_sha1);
        update->flags = flags;
        update->have_old = 1;
        hashcpy(update->new_sha1, new_sha1);
        hashclr(update->old_sha1);
        update->flags = flags;
        update->have_old = 1;

+       return 0;

 }
 
 void ref_transaction_delete(struct ref_transaction *transaction,
 }
 
 void ref_transaction_delete(struct ref_transaction *transaction,

diff --git a/refs.h b/refs.h
index c5376cee8d84f94ad2e08ce5baae7537e9d4a47a..b648819a2fc61c6989eb8ee42dedf6afc17bfdbb 100644 (file)
--- a/refs.h
+++ b/refs.h
@@ -10,6 +10,38 @@ struct ref_lock {
        int force_write;
 };
 
        int force_write;
 };
 

+/*
+ * A ref_transaction represents a collection of ref updates
+ * that should succeed or fail together.
+ *
+ * Calling sequence
+ * ----------------
+ * - Allocate and initialize a `struct ref_transaction` by calling
+ *   `ref_transaction_begin()`.
+ *
+ * - List intended ref updates by calling functions like
+ *   `ref_transaction_update()` and `ref_transaction_create()`.
+ *
+ * - Call `ref_transaction_commit()` to execute the transaction.
+ *   If this succeeds, the ref updates will have taken place and
+ *   the transaction cannot be rolled back.
+ *
+ * - At any time call `ref_transaction_free()` to discard the
+ *   transaction and free associated resources.  In particular,
+ *   this rolls back the transaction if it has not been
+ *   successfully committed.
+ *
+ * Error handling
+ * --------------
+ *
+ * On error, transaction functions append a message about what
+ * went wrong to the 'err' argument.  The message mentions what
+ * ref was being updated (if any) when the error occurred so it
+ * can be passed to 'die' or 'error' as-is.
+ *
+ * The message is appended to err without first clearing err.
+ * err will not be '\n' terminated.
+ */

 struct ref_transaction;
 
 /*
 struct ref_transaction;
 
 /*


@@ -248,7 +280,7 @@ struct ref_transaction *ref_transaction_begin(void);
  * it must not have existed beforehand.
  * Function returns 0 on success and non-zero on failure. A failure to update
  * means that the transaction as a whole has failed and will need to be
  * it must not have existed beforehand.
  * Function returns 0 on success and non-zero on failure. A failure to update
  * means that the transaction as a whole has failed and will need to be

- * rolled back. On failure the err buffer will be updated.
+ * rolled back.

  */
 int ref_transaction_update(struct ref_transaction *transaction,
                           const char *refname,
  */
 int ref_transaction_update(struct ref_transaction *transaction,
                           const char *refname,


@@ -262,11 +294,15 @@ int ref_transaction_update(struct ref_transaction *transaction,
  * that the reference should have after the update; it must not be the
  * null SHA-1.  It is verified that the reference does not exist
  * already.
  * that the reference should have after the update; it must not be the
  * null SHA-1.  It is verified that the reference does not exist
  * already.

+ * Function returns 0 on success and non-zero on failure. A failure to create
+ * means that the transaction as a whole has failed and will need to be
+ * rolled back.

  */
  */

-void ref_transaction_create(struct ref_transaction *transaction,
-                           const char *refname,
-                           const unsigned char *new_sha1,
-                           int flags);
+int ref_transaction_create(struct ref_transaction *transaction,
+                          const char *refname,
+                          const unsigned char *new_sha1,
+                          int flags,
+                          struct strbuf *err);

 
 /*
  * Add a reference deletion to transaction.  If have_old is true, then
 
 /*
  * Add a reference deletion to transaction.  If have_old is true, then


@@ -282,8 +318,6 @@ void ref_transaction_delete(struct ref_transaction *transaction,
  * Commit all of the changes that have been queued in transaction, as
  * atomically as possible.  Return a nonzero value if there is a
  * problem.
  * Commit all of the changes that have been queued in transaction, as
  * atomically as possible.  Return a nonzero value if there is a
  * problem.

- * If err is non-NULL we will add an error string to it to explain why
- * the transaction failed. The string does not end in newline.

  */
 int ref_transaction_commit(struct ref_transaction *transaction,
                           const char *msg, struct strbuf *err);
  */
 int ref_transaction_commit(struct ref_transaction *transaction,
                           const char *msg, struct strbuf *err);