Add --list-repos-only flag

Author: mheap

README.md

@@ -43,13 +43,14 @@ Run with the `--verbose` flag to see debug information
 
 ## Options
 
-| Flag          | Description                                                    | Default |
-| ------------- | -------------------------------------------------------------- | ------- |
-| --pat <token> | GitHub API Token                                               | N/A     |
-| --dry-run     | Output log messages only. Do not make any changes              | N/A     |
-| --repo <name> | The repo to update (format: user/repo)                         | N/A     |
-| --user <name> | Update all repos owned by the provided user (example: my-user) | N/A     |
-| --org <name>  | Update all repos in the provided org (example: my-org-name)    | N/A     |
-| --keep-old    | Keep the old branch rather than deleting it                    | false   |
-| --old         | The name of the branch to rename                               | master  |
-| --new         | The new branch name                                            | main    |
+| Flag              | Description                                                    | Default |
+| ----------------- | -------------------------------------------------------------- | ------- |
+| --pat <token>     | GitHub API Token                                               | N/A     |
+| --repo <name>     | The repo to update (format: user/repo)                         | N/A     |
+| --user <name>     | Update all repos owned by the provided user (example: my-user) | N/A     |
+| --org <name>      | Update all repos in the provided org (example: my-org-name)    | N/A     |
+| --keep-old        | Keep the old branch rather than deleting it                    | false   |
+| --dry-run         | Output log messages only. Do not make any changes              | false   |
+| --list-repos-only | List repos that would be affected, then exit                   | false   |
+| --old             | The name of the branch to rename                               | master  |
+| --new             | The new branch name                                            | main    |

bin/github-default-branch

@@ -53,6 +53,11 @@
 
   const repos = await getRepos(argv, octokit);
 
+  if (argv.listReposOnly) {
+    console.log(repos.join("\n"));
+    return;
+  }
+
   const old = argv.old || "master";
   const target = argv.new || "main";