Discover refs via smart HTTP server when available

Instead of loading the cached info/refs, try to use the smart HTTP
version when the server supports it.  Since the smart variant is
actually the pkt-line stream from the start of either upload-pack
or receive-pack we need to parse these through get_remote_heads,
which requires a background thread to feed its pipe.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
CC: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/remote-curl.c b/remote-curl.c
index 5c9dd97d1da1f4896ebd3d9c5296308bd912d1e7..3917d45deb782b0da438a4d70db2af8c1e2c6859 100644 (file)
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -5,6 +5,7 @@
 #include "http.h"
 #include "exec_cmd.h"
 #include "run-command.h"
+#include "pkt-line.h"
 
 static struct remote *remote;
 static const char *url;
@@ -75,21 +76,46 @@ static int set_option(const char *name, const char *value)
        }
 }
 
-static struct ref *get_refs(void)
+struct discovery {
+       const char *service;
+       char *buf_alloc;
+       char *buf;
+       size_t len;
+       unsigned proto_git : 1;
+};
+static struct discovery *last_discovery;
+
+static void free_discovery(struct discovery *d)
+{
+       if (d) {
+               if (d == last_discovery)
+                       last_discovery = NULL;
+               free(d->buf_alloc);
+               free(d);
+       }
+}
+
+static struct discovery* discover_refs(const char *service)
 {
        struct strbuf buffer = STRBUF_INIT;
-       char *data, *start, *mid;
-       char *ref_name;
+       struct discovery *last = last_discovery;
        char *refs_url;
-       int i = 0;
-       int http_ret;
+       int http_ret, is_http = 0;
 
-       struct ref *refs = NULL;
-       struct ref *ref = NULL;
-       struct ref *last_ref = NULL;
+       if (last && !strcmp(service, last->service))
+               return last;
+       free_discovery(last);
 
-       refs_url = xmalloc(strlen(url) + 11);
-       sprintf(refs_url, "%s/info/refs", url);
+       strbuf_addf(&buffer, "%s/info/refs", url);
+       if (!prefixcmp(url, "http://") || !prefixcmp(url, "https://")) {
+               is_http = 1;
+               if (!strchr(url, '?'))
+                       strbuf_addch(&buffer, '?');
+               else
+                       strbuf_addch(&buffer, '&');
+               strbuf_addf(&buffer, "service=%s", service);
+       }
+       refs_url = strbuf_detach(&buffer, NULL);
 
        init_walker();
        http_ret = http_get_strbuf(refs_url, &buffer, HTTP_NO_CACHE);
@@ -104,10 +130,86 @@ static struct ref *get_refs(void)
                die("HTTP request failed");
        }
 
-       data = buffer.buf;
+       last= xcalloc(1, sizeof(*last_discovery));
+       last->service = service;
+       last->buf_alloc = strbuf_detach(&buffer, &last->len);
+       last->buf = last->buf_alloc;
+
+       if (is_http && 5 <= last->len && last->buf[4] == '#') {
+               /* smart HTTP response; validate that the service
+                * pkt-line matches our request.
+                */
+               struct strbuf exp = STRBUF_INIT;
+
+               if (packet_get_line(&buffer, &last->buf, &last->len) <= 0)
+                       die("%s has invalid packet header", refs_url);
+               if (buffer.len && buffer.buf[buffer.len - 1] == '\n')
+                       strbuf_setlen(&buffer, buffer.len - 1);
+
+               strbuf_addf(&exp, "# service=%s", service);
+               if (strbuf_cmp(&exp, &buffer))
+                       die("invalid server response; got '%s'", buffer.buf);
+               strbuf_release(&exp);
+
+               /* The header can include additional metadata lines, up
+                * until a packet flush marker.  Ignore these now, but
+                * in the future we might start to scan them.
+                */
+               strbuf_reset(&buffer);
+               while (packet_get_line(&buffer, &last->buf, &last->len) > 0)
+                       strbuf_reset(&buffer);
+
+               last->proto_git = 1;
+       }
+
+       free(refs_url);
+       strbuf_release(&buffer);
+       last_discovery = last;
+       return last;
+}
+
+static int write_discovery(int fd, void *data)
+{
+       struct discovery *heads = data;
+       int err = 0;
+       if (write_in_full(fd, heads->buf, heads->len) != heads->len)
+               err = 1;
+       close(fd);
+       return err;
+}
+
+static struct ref *parse_git_refs(struct discovery *heads)
+{
+       struct ref *list = NULL;
+       struct async async;
+
+       memset(&async, 0, sizeof(async));
+       async.proc = write_discovery;
+       async.data = heads;
+
+       if (start_async(&async))
+               die("cannot start thread to parse advertised refs");
+       get_remote_heads(async.out, &list, 0, NULL, 0, NULL);
+       close(async.out);
+       if (finish_async(&async))
+               die("ref parsing thread failed");
+       return list;
+}
+
+static struct ref *parse_info_refs(struct discovery *heads)
+{
+       char *data, *start, *mid;
+       char *ref_name;
+       int i = 0;
+
+       struct ref *refs = NULL;
+       struct ref *ref = NULL;
+       struct ref *last_ref = NULL;
+
+       data = heads->buf;
        start = NULL;
        mid = data;
-       while (i < buffer.len) {
+       while (i < heads->len) {
                if (!start) {
                        start = &data[i];
                }
@@ -131,8 +233,7 @@ static struct ref *get_refs(void)
                i++;
        }
 
-       strbuf_release(&buffer);
-
+       init_walker();
        ref = alloc_ref("HEAD");
        if (!walker->fetch_ref(walker, ref) &&
            !resolve_remote_symref(ref, refs)) {
@@ -142,11 +243,23 @@ static struct ref *get_refs(void)
                free(ref);
        }
 
-       strbuf_release(&buffer);
-       free(refs_url);
        return refs;
 }
 
+static struct ref *get_refs(int for_push)
+{
+       struct discovery *heads;
+
+       if (for_push)
+               heads = discover_refs("git-receive-pack");
+       else
+               heads = discover_refs("git-upload-pack");
+
+       if (heads->proto_git)
+               return parse_git_refs(heads);
+       return parse_info_refs(heads);
+}
+
 static void output_refs(struct ref *refs)
 {
        struct ref *posn;
@@ -317,7 +430,8 @@ int main(int argc, const char **argv)
                        parse_fetch(&buf);
 
                } else if (!strcmp(buf.buf, "list") || !prefixcmp(buf.buf, "list ")) {
-                       output_refs(get_refs());
+                       int for_push = !!strstr(buf.buf + 4, "for-push");
+                       output_refs(get_refs(for_push));
 
                } else if (!prefixcmp(buf.buf, "push ")) {
                        parse_push(&buf);