[PATCH 03/12] for_each_alternate_ref: use strbuf for path allocation

[Jeff King <peff@peff.net>]

We have a string with ".../objects" pointing to the
alternate object store, and overwrite bits of it to look at
other paths in the (potential) git repository holding it.
This works because the only path we care about is "refs",
which is shorter than "objects".

Using a strbuf to hold the path lets us get rid of some
magic numbers, and makes it more obvious that the memory
operations are safe.

Signed-off-by: Jeff King <peff@peff.net>
---
I had thought I was going to need to generate more paths in the
alternate repo, but I ended up not needing to. So this was originally
done to make that easier, but I think it stands on its own as a cleanup.

 transport.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/transport.c b/transport.c
index 6b4b3ed31..594533d88 100644
--- a/transport.c
+++ b/transport.c
@@ -1207,34 +1207,34 @@ struct alternate_refs_data {
 static int refs_from_alternate_cb(struct alternate_object_database *e,
 				  void *data)
 {
-	char *other;
-	size_t len;
+	struct strbuf path = STRBUF_INIT;
+	size_t base_len;
 	struct remote *remote;
 	struct transport *transport;
 	const struct ref *extra;
 	struct alternate_refs_data *cb = data;
 
-	other = real_pathdup(e->path);
-	if (!other)
-		return 0;
-	len = strlen(other);
-
-	if (len < 8 || memcmp(other + len - 8, "/objects", 8))
+	if (!strbuf_realpath(&path, e->path, 0))
+		goto out;
+	if (!strbuf_strip_suffix(&path, "/objects"))
 		goto out;
+	base_len = path.len;
+
 	/* Is this a git repository with refs? */
-	memcpy(other + len - 8, "/refs", 6);
-	if (!is_directory(other))
+	strbuf_addstr(&path, "/refs");
+	if (!is_directory(path.buf))
 		goto out;
-	other[len - 8] = '\0';
-	remote = remote_get(other);
-	transport = transport_get(remote, other);
+	strbuf_setlen(&path, base_len);
+
+	remote = remote_get(path.buf);
+	transport = transport_get(remote, path.buf);
 	for (extra = transport_get_remote_refs(transport);
 	     extra;
 	     extra = extra->next)
 		cb->fn(extra, cb->data);
 	transport_disconnect(transport);
 out:
-	free(other);
+	strbuf_release(&path);
 	return 0;
 }
 
-- 
2.11.0.765.g454d2182f