git fetch-pack: add --diag-url

The main purpose is to trace the URL parser called by git_connect() in
connect.c

The main features of the parser can be listed as this:

- parse out host and path for URLs with a scheme (git:// file:// ssh://)
- parse host names embedded by [] correctly
- extract the port number, if present
- separate URLs like "file" (which are local)
  from URLs like "host:repo" which should use ssh

Add the new parameter "--diag-url" to "git fetch-pack", which prints
the value for protocol, host and path to stderr and exits.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fetch-pack.c

@@ -7,7 +7,7 @@
 static const char fetch_pack_usage[] =
 "git fetch-pack [--all] [--stdin] [--quiet|-q] [--keep|-k] [--thin] "
 "[--include-tag] [--upload-pack=<git-upload-pack>] [--depth=<n>] "
-"[--no-progress] [-v] [<host>:]<directory> [<refs>...]";
+"[--no-progress] [--diag-url] [-v] [<host>:]<directory> [<refs>...]";
 
 static void add_sought_entry_mem(struct ref ***sought, int *nr, int *alloc,
 				 const char *name, int namelen)
@@ -81,6 +81,10 @@ int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
 			args.stdin_refs = 1;
 			continue;
 		}
+		if (!strcmp("--diag-url", arg)) {
+			args.diag_url = 1;
+			continue;
+		}
 		if (!strcmp("-v", arg)) {
 			args.verbose = 1;
 			continue;
@@ -146,10 +150,14 @@ int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
 		fd[0] = 0;
 		fd[1] = 1;
 	} else {
+		int flags = args.verbose ? CONNECT_VERBOSE : 0;
+		if (args.diag_url)
+			flags |= CONNECT_DIAG_URL;
 		conn = git_connect(fd, dest, args.uploadpack,
-				   args.verbose ? CONNECT_VERBOSE : 0);
+				   flags);
+		if (!conn)
+			return args.diag_url ? 0 : 1;
 	}
-
 	get_remote_heads(fd[0], NULL, 0, &ref, 0, NULL);
 
 	ref = fetch_pack(&args, fd, conn, ref, dest,

connect.c

@@ -236,6 +236,20 @@ enum protocol {
 	PROTO_GIT
 };
 
+static const char *prot_name(enum protocol protocol)
+{
+	switch (protocol) {
+		case PROTO_LOCAL:
+			return "file";
+		case PROTO_SSH:
+			return "ssh";
+		case PROTO_GIT:
+			return "git";
+		default:
+			return "unkown protocol";
+	}
+}
+
 static enum protocol get_protocol(const char *name)
 {
 	if (!strcmp(name, "ssh"))
@@ -670,6 +684,20 @@ struct child_process *git_connect(int fd[2], const char *url,
 	signal(SIGCHLD, SIG_DFL);
 
 	protocol = parse_connect_url(url, &host, &port, &path);
+	if (flags & CONNECT_DIAG_URL) {
+		printf("Diag: url=%s\n", url ? url : "NULL");
+		printf("Diag: protocol=%s\n", prot_name(protocol));
+		printf("Diag: hostandport=%s", host ? host : "NULL");
+		if (port)
+			printf(":%s\n", port);
+		else
+			printf("\n");
+		printf("Diag: path=%s\n", path ? path : "NULL");
+		free(host);
+		free(port);
+		free(path);
+		return NULL;
+	}
 
 	if (protocol == PROTO_GIT) {
 		/* These underlying connection commands die() if they

connect.h

@@ -2,6 +2,7 @@
 #define CONNECT_H
 
 #define CONNECT_VERBOSE       (1u << 0)
+#define CONNECT_DIAG_URL      (1u << 1)
 extern struct child_process *git_connect(int fd[2], const char *url, const char *prog, int flags);
 extern int finish_connect(struct child_process *conn);
 extern int git_connection_is_socket(struct child_process *conn);

fetch-pack.h

@@ -14,6 +14,7 @@ struct fetch_pack_args {
 		use_thin_pack:1,
 		fetch_all:1,
 		stdin_refs:1,
+		diag_url:1,
 		verbose:1,
 		no_progress:1,
 		include_tag:1,