feat(repo): sync forks on the server, wire forks into clones, validate set-default

repo sync OWNER/REPO, run where no Git remote points to the repository,
now updates it on the server: a fork's branch fast-forwards to its
parent's through merge-upstream, and a pull mirror fetches its source.

repo fork reports an existing fork ("! bob/x already exists") instead of
a raw HTTP 409, refuses to fork a repository into its own owner, and
gains --fork-name, --clone (Git flags after --) and --remote, which adds
the fork as origin and renames the old origin to upstream.

repo clone passes Git flags after --, and takes --upstream-remote-name
and --no-upstream for forks. Clones report what they set up.

repo set-default checks that the repository exists before saving it,
prints the saved repository with --view, removes it with --unset, and
reports the change.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/repos.go

@@ -51,22 +51,83 @@ func (a *application) repoCommand() *cobra.Command {
 		Long: `Work with Gitea repositories: list and view them, create, fork, clone and migrate them, keep
 local branches and forks in sync, and change their settings.`,
 	}
-	group.AddCommand(a.repoListCommand(), a.repoViewCommand(), a.repositorySyncCommand())
-	group.AddCommand(&cobra.Command{Use: "set-default [repository]", Short: "Save the selected repository in local Git configuration", Annotations: textOutput("set-default configures Git"), Args: usageArgs(cobra.MaximumNArgs(1)), RunE: func(cmd *cobra.Command, args []string) error {
-		if err := a.repositoryArgument(args); err != nil {
-			return err
-		}
-		target, err := a.resolve(cmd.Context(), true)
-		if err != nil {
-			return err
-		}
-		_, err = a.git(cmd.Context(), "config", "--local", "tea.repository", target.Host+"/"+target.Repo)
-		return err
-	}})
+	group.AddCommand(a.repoListCommand(), a.repoViewCommand(), a.repositorySyncCommand(), a.repoSetDefaultCommand())
 	a.addRepositoryMutations(group)
 	return group
 }
 
+func (a *application) repoSetDefaultCommand() *cobra.Command {
+	var view, unset bool
+	command := &cobra.Command{
+		Use:   "set-default [<repository>]",
+		Short: "Set the default repository for this clone",
+		Long: `Set the repository that tea commands use in the current Git clone, instead of the one found through
+its Git remotes. It is saved as tea.repository in the clone's Git configuration.
+
+Without an argument, the repository that tea selects now is saved.`,
+		Example: `# Make tea commands in this clone use the fork's parent
+$ tea repo set-default alice/project
+
+# Show the saved repository
+$ tea repo set-default --view
+
+# Go back to the repository of the Git remotes
+$ tea repo set-default --unset`,
+		Annotations: map[string]string{"tea.arguments": repositoryArguments, "tea.text": "set-default configures Git"},
+		Args:        usageArgs(cobra.MaximumNArgs(1)),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			switch {
+			case view && unset:
+				return clierr.Wrap(clierr.Usage, errors.New("--view and --unset cannot be combined"))
+			case (view || unset) && len(args) > 0:
+				return clierr.Wrap(clierr.Usage, errors.New("--view and --unset take no repository"))
+			}
+			ctx := cmd.Context()
+			if inside, _ := a.gitProbe().Output(ctx, a.options.cwd, false, "rev-parse", "--is-inside-work-tree"); inside != "true" {
+				return clierr.Wrap(clierr.Usage, errors.New("set-default must run inside a Git clone"))
+			}
+			saved, _ := a.gitProbe().Output(ctx, a.options.cwd, false, "config", "--local", "--get", "tea.repository")
+			switch {
+			case view && saved == "":
+				_, err := fmt.Fprintln(cmd.ErrOrStderr(), "no default repository is set for this clone")
+				return err
+			case view:
+				_, err := fmt.Fprintln(cmd.OutOrStdout(), terminal.SafeLine(saved))
+				return err
+			case unset && saved == "":
+				a.warn(cmd, "No default repository is set for this clone")
+				return nil
+			case unset:
+				if _, err := a.git(ctx, "config", "--local", "--unset", "tea.repository"); err != nil {
+					return err
+				}
+				a.done(cmd, "Removed the default repository %s from this clone", saved)
+				return nil
+			}
+			if err := a.repositoryArgument(args); err != nil {
+				return err
+			}
+			t, err := a.resolve(ctx, true)
+			if err != nil {
+				return err
+			}
+			item, err := (services.Repositories{Client: t.client}).View(ctx, t.Repo)
+			if err != nil {
+				return err
+			}
+			if _, err := a.git(ctx, "config", "--local", "tea.repository", t.Host+"/"+item.FullName); err != nil {
+				return err
+			}
+			a.done(cmd, "Set %s as the default repository for this clone", item.FullName)
+			return nil
+		},
+	}
+	command.Flags().BoolVarP(&view, "view", "v", false, "Print the saved default repository")
+	command.Flags().BoolVarP(&unset, "unset", "u", false, "Remove the saved default repository")
+	command.ValidArgsFunction = a.completeRepos()
+	return command
+}
+
 func (a *application) repoListCommand() *cobra.Command {
 	var opts services.RepositoryListOptions
 	list := &cobra.Command{