http: use idempotent git_hash_discard()

Now that it is OK to call git_hash_discard() even after finalizing the
hash, we no longer need the ctx_valid bool added by a2d8ea5a76 (http:
discard hash in dumb-http http_object_request, 2026-07-02).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http.c

@@ -2880,7 +2880,6 @@ struct http_object_request *new_http_object_request(const char *base_url,
 	git_inflate_init(&freq->stream);
 
 	git_hash_init(&freq->c, the_hash_algo);
-	freq->hash_ctx_valid = 1;
 
 	freq->url = get_remote_object_url(base_url, hex, 0);
 
@@ -2989,7 +2988,6 @@ int finish_http_object_request(struct http_object_request *freq)
 	}
 
 	git_hash_final_oid(&freq->real_oid, &freq->c);
-	freq->hash_ctx_valid = 0;
 	if (freq->zret != Z_STREAM_END) {
 		unlink_or_warn(freq->tmpfile.buf);
 		return -1;
@@ -3030,8 +3028,7 @@ void release_http_object_request(struct http_object_request **freq_p)
 	curl_slist_free_all(freq->headers);
 	strbuf_release(&freq->tmpfile);
 	git_inflate_end(&freq->stream);
-	if (freq->hash_ctx_valid)
-		git_hash_discard(&freq->c);
+	git_hash_discard(&freq->c);
 
 	free(freq);
 	*freq_p = NULL;

http.h

@@ -255,7 +255,6 @@ struct http_object_request {
 	struct object_id oid;
 	struct object_id real_oid;
 	struct git_hash_ctx c;
-	int hash_ctx_valid;
 	git_zstream stream;
 	int zret;
 	int rename;