refs_verify_refname_available(): implement once for all backends

It turns out that we can now implement
`refs_verify_refname_available()` based on the other virtual
functions, so there is no need for it to be defined at the backend
level. Instead, define it once in `refs.c` and remove the
`files_backend` definition.

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

1 files changed, 83 insertions, 2 deletions

diff --git a/refs.c b/refs.c
index 2ae18097d4..e841248b01 100644
--- a/refs.c
+++ b/refs.c
@@ -5,6 +5,7 @@
 #include "cache.h"
 #include "hashmap.h"
 #include "lockfile.h"
+#include "iterator.h"
 #include "refs.h"
 #include "refs/refs-internal.h"
 #include "object.h"
@@ -1658,11 +1659,91 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 
 int refs_verify_refname_available(struct ref_store *refs,
 				  const char *refname,
-				  const struct string_list *extra,
+				  const struct string_list *extras,
 				  const struct string_list *skip,
 				  struct strbuf *err)
 {
-	return refs->be->verify_refname_available(refs, refname, extra, skip, err);
+	const char *slash;
+	const char *extra_refname;
+	struct strbuf dirname = STRBUF_INIT;
+	struct strbuf referent = STRBUF_INIT;
+	struct object_id oid;
+	unsigned int type;
+	struct ref_iterator *iter;
+	int ok;
+	int ret = -1;
+
+	/*
+	 * For the sake of comments in this function, suppose that
+	 * refname is "refs/foo/bar".
+	 */
+
+	assert(err);
+
+	strbuf_grow(&dirname, strlen(refname) + 1);
+	for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) {
+		/* Expand dirname to the new prefix, not including the trailing slash: */
+		strbuf_add(&dirname, refname + dirname.len, slash - refname - dirname.len);
+
+		/*
+		 * We are still at a leading dir of the refname (e.g.,
+		 * "refs/foo"; if there is a reference with that name,
+		 * it is a conflict, *unless* it is in skip.
+		 */
+		if (skip && string_list_has_string(skip, dirname.buf))
+			continue;
+
+		if (!refs_read_raw_ref(refs, dirname.buf, oid.hash, &referent, &type)) {
+			strbuf_addf(err, "'%s' exists; cannot create '%s'",
+				    dirname.buf, refname);
+			goto cleanup;
+		}
+
+		if (extras && string_list_has_string(extras, dirname.buf)) {
+			strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
+				    refname, dirname.buf);
+			goto cleanup;
+		}
+	}
+
+	/*
+	 * We are at the leaf of our refname (e.g., "refs/foo/bar").
+	 * There is no point in searching for a reference with that
+	 * name, because a refname isn't considered to conflict with
+	 * itself. But we still need to check for references whose
+	 * names are in the "refs/foo/bar/" namespace, because they
+	 * *do* conflict.
+	 */
+	strbuf_addstr(&dirname, refname + dirname.len);
+	strbuf_addch(&dirname, '/');
+
+	iter = refs_ref_iterator_begin(refs, dirname.buf, 0,
+				       DO_FOR_EACH_INCLUDE_BROKEN);
+	while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
+		if (skip &&
+		    string_list_has_string(skip, iter->refname))
+			continue;
+
+		strbuf_addf(err, "'%s' exists; cannot create '%s'",
+			    iter->refname, refname);
+		ref_iterator_abort(iter);
+		goto cleanup;
+	}
+
+	if (ok != ITER_DONE)
+		die("BUG: error while iterating over references");
+
+	extra_refname = find_descendant_ref(dirname.buf, extras, skip);
+	if (extra_refname)
+		strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
+			    refname, extra_refname);
+	else
+		ret = 0;
+
+cleanup:
+	strbuf_release(&referent);
+	strbuf_release(&dirname);
+	return ret;
 }
 
 int refs_for_each_reflog(struct ref_store *refs, each_ref_fn fn, void *cb_data)