fix(git): tolerate remotes without a url key

git-annex S3 special remotes have no url key; running
`git config --get-all remote.<name>.url` on them exits 1, which made
tea hard-fail in Config() on any repo that has such a remote. Treat a
missing key (exit 1 with empty or 'No such section or key' stderr) as an
empty URL list, mirroring the existing branch-section handling.

modules/git/cli_backend.go

@@ -73,8 +73,16 @@ func (r *cliRepository) Config() (*Config, error) {
 	for _, remoteName := range strings.Fields(remoteOut) {
 		urlOut, err := r.git(nil, nil, "config", "--get-all", "remote."+remoteName+".url")
 		if err != nil {
+			// tolerate remotes without a url key (e.g. git-annex special remotes)
+			var gitErr *gitCommandError
+			if !errors.As(err, &gitErr) {
 				return nil, err
 			}
+			stderr := strings.TrimSpace(gitErr.stderr)
+			if stderr != "" && !strings.Contains(stderr, "No such section or key") {
+				return nil, err
+			}
+		}
 		cfg.Remotes[remoteName] = &RemoteConfig{Name: remoteName, URLs: splitNonEmptyLines(urlOut)}
 	}