remote-svn: add incremental import

Search for a note attached to the ref to update and read it's
'Revision-number:'-line. Start import from the next svn revision.

If there is no next revision in the svn repo, svnrdump terminates with
a message on stderr an non-zero return value. This looks a little
weird, but there is no other way to know whether there is a new
revision in the svn repo.

On the start of an incremental import, the parent of the first commit
in the fast-import stream is set to the branch name to update. All
following commits specify their parent by a mark number. Previous mark
files are currently not reused.

Signed-off-by: Florian Achleitner <florian.achleitner.2.6.31@gmail.com>
Acked-by: David Michael Barr <b@rr-dav.id.au>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 75 insertions, 4 deletions

diff --git a/remote-testsvn.c b/remote-testsvn.c
index 45eba9f2d9..b741f6d9a7 100644
--- a/remote-testsvn.c
+++ b/remote-testsvn.c
@@ -12,7 +12,8 @@ static const char *url;
 static int dump_from_file;
 static const char *private_ref;
 static const char *remote_ref = "refs/heads/master";
-static const char *marksfilename;
+static const char *marksfilename, *notes_ref;
+struct rev_note { unsigned int rev_nr; };
 
 static int cmd_capabilities(const char *line);
 static int cmd_import(const char *line);
@@ -48,14 +49,79 @@ static void terminate_batch(void)
 	fflush(stdout);
 }
 
+/* NOTE: 'ref' refers to a git reference, while 'rev' refers to a svn revision. */
+static char *read_ref_note(const unsigned char sha1[20])
+{
+	const unsigned char *note_sha1;
+	char *msg = NULL;
+	unsigned long msglen;
+	enum object_type type;
+
+	init_notes(NULL, notes_ref, NULL, 0);
+	if (!(note_sha1 = get_note(NULL, sha1)))
+		return NULL;	/* note tree not found */
+	if (!(msg = read_sha1_file(note_sha1, &type, &msglen)))
+		error("Empty notes tree. %s", notes_ref);
+	else if (!msglen || type != OBJ_BLOB) {
+		error("Note contains unusable content. "
+			"Is something else using this notes tree? %s", notes_ref);
+		free(msg);
+		msg = NULL;
+	}
+	free_notes(NULL);
+	return msg;
+}
+
+static int parse_rev_note(const char *msg, struct rev_note *res)
+{
+	const char *key, *value, *end;
+	size_t len;
+
+	while (*msg) {
+		end = strchr(msg, '\n');
+		len = end ? end - msg : strlen(msg);
+
+		key = "Revision-number: ";
+		if (!prefixcmp(msg, key)) {
+			long i;
+			char *end;
+			value = msg + strlen(key);
+			i = strtol(value, &end, 0);
+			if (end == value || i < 0 || i > UINT32_MAX)
+				return -1;
+			res->rev_nr = i;
+		}
+		msg += len + 1;
+	}
+	return 0;
+}
+
 static int cmd_import(const char *line)
 {
 	int code;
 	int dumpin_fd;
-	unsigned int startrev = 0;
+	char *note_msg;
+	unsigned char head_sha1[20];
+	unsigned int startrev;
 	struct argv_array svndump_argv = ARGV_ARRAY_INIT;
 	struct child_process svndump_proc;
 
+	if (read_ref(private_ref, head_sha1))
+		startrev = 0;
+	else {
+		note_msg = read_ref_note(head_sha1);
+		if(note_msg == NULL) {
+			warning("No note found for %s.", private_ref);
+			startrev = 0;
+		} else {
+			struct rev_note note = { 0 };
+			if (parse_rev_note(note_msg, &note))
+				die("Revision number couldn't be parsed from note.");
+			startrev = note.rev_nr + 1;
+			free(note_msg);
+		}
+	}
+
 	if (dump_from_file) {
 		dumpin_fd = open(url, O_RDONLY);
 		if(dumpin_fd < 0)
@@ -79,7 +145,7 @@ static int cmd_import(const char *line)
 			"feature export-marks=%s\n", marksfilename, marksfilename);
 
 	svndump_init_fd(dumpin_fd, STDIN_FILENO);
-	svndump_read(url, private_ref);
+	svndump_read(url, private_ref, notes_ref);
 	svndump_deinit();
 	svndump_reset();
 
@@ -150,7 +216,8 @@ static int do_command(struct strbuf *line)
 int main(int argc, const char **argv)
 {
 	struct strbuf buf = STRBUF_INIT, url_sb = STRBUF_INIT,
-			private_ref_sb = STRBUF_INIT, marksfilename_sb = STRBUF_INIT;
+			private_ref_sb = STRBUF_INIT, marksfilename_sb = STRBUF_INIT,
+			notes_ref_sb = STRBUF_INIT;
 	static struct remote *remote;
 	const char *url_in;
 
@@ -176,6 +243,9 @@ int main(int argc, const char **argv)
 	strbuf_addf(&private_ref_sb, "refs/svn/%s/master", remote->name);
 	private_ref = private_ref_sb.buf;
 
+	strbuf_addf(&notes_ref_sb, "refs/notes/%s/revs", remote->name);
+	notes_ref = notes_ref_sb.buf;
+
 	strbuf_addf(&marksfilename_sb, "%s/info/fast-import/remote-svn/%s.marks",
 		get_git_dir(), remote->name);
 	marksfilename = marksfilename_sb.buf;
@@ -195,6 +265,7 @@ int main(int argc, const char **argv)
 	strbuf_release(&buf);
 	strbuf_release(&url_sb);
 	strbuf_release(&private_ref_sb);
+	strbuf_release(&notes_ref_sb);
 	strbuf_release(&marksfilename_sb);
 	return 0;
 }