Introduce a new function `ref_transaction_update_reflog`, for clients to
add a reflog update to a transaction. While the existing function
`ref_transaction_update` also allows clients to add a reflog entry, this
function does a few things more, It:
- Enforces that only a reflog entry is added and does not update the
ref itself.
- Allows the users to also provide the committer information. This
means clients can add reflog entries with custom committer
information.
The `transaction_refname_valid()` function also modifies the error
message selectively based on the type of the update. This change also
affects reflog updates which go through `ref_transaction_update()`.
A follow up commit will utilize this function to add reflog support to
`git refs migrate`.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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