scan_path(): Improve handling of inaccessible directories

When scanning a tree containing inaccessible directories (e.g. '.ssh'
directories in users' homedirs, or repos with explicitly restricted access),
scan_path() currently causes three lines of "Permissions denied" errors to be
printed to the CGI error log per inaccessible directory:

  Error checking path /home/foo/.ssh: Permission denied (13)
  Error checking path /home/foo/.ssh/.git: Permission denied (13)
  Error opening directory /home/foo/.ssh: Permission denied (13)

This is a side-effect of calling is_git_dir(path) and
is_git_dir(fmt("%s/.git", path) _before_ we try to opendir(path).

By placing the opendir(path) before the two is_git_dir() calls, we reduce the
noise to a single line per inaccessible directory:

  Error opening directory /home/foo/.ssh: Permission denied (13)

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Lars Hjemli <larsh@prediktor.no>

scan-tree.c

@@ -159,24 +159,23 @@ static void add_repo(const char *base, const char *path, repo_config_fn fn)
 
 static void scan_path(const char *base, const char *path, repo_config_fn fn)
 {
-	DIR *dir;
+	DIR *dir = opendir(path);
 	struct dirent *ent;
 	char *buf;
 	struct stat st;
 
+	if (!dir) {
+		fprintf(stderr, "Error opening directory %s: %s (%d)\n",
+			path, strerror(errno), errno);
+		return;
+	}
 	if (is_git_dir(path)) {
 		add_repo(base, path, fn);
-		return;
+		goto end;
 	}
 	if (is_git_dir(fmt("%s/.git", path))) {
 		add_repo(base, fmt("%s/.git", path), fn);
-		return;
-	}
-	dir = opendir(path);
-	if (!dir) {
-		fprintf(stderr, "Error opening directory %s: %s (%d)\n",
-			path, strerror(errno), errno);
-		return;
+		goto end;
 	}
 	while((ent = readdir(dir)) != NULL) {
 		if (ent->d_name[0] == '.') {
@@ -202,6 +201,7 @@ static void scan_path(const char *base, const char *path, repo_config_fn fn)
 			scan_path(base, buf, fn);
 		free(buf);
 	}
+end:
 	closedir(dir);
 }