src/main/java/nl/andrewlalis/Main.java

@@ -41,6 +41,7 @@ public class Main {
         executor.registerCommand("delete_repos", new DeleteRepos());
         executor.registerCommand("delegate_student_teams", new DelegateStudentTeams(app));
         executor.registerCommand("setup_student_repos", new SetupStudentRepos(app));
+        executor.registerCommand("list_repos", new ListRepos());
 
         logger.info("GithubManager for Github Repositories in Educational Organizations.\n" +
                 "© Andrew Lalis (2018), All rights reserved.\n" +

src/main/java/nl/andrewlalis/git_api/GithubManager.java

@@ -51,6 +51,28 @@ public class GithubManager {
         }
     }
 
+    /**
+     * Returns a list of repositories with the given substring.
+     * @param substring A string which all repositories should contain.
+     * @return A List of repositories whose names contain the given substring.
+     */
+    public List<GHRepository> listReposWithPrefix(String substring) {
+        List<GHRepository> repos = new ArrayList<>();
+        try {
+            List<GHRepository> allRepos = this.organization.listRepositories().asList();
+            for (GHRepository repo : allRepos) {
+                if (repo.getName().contains(substring)) {
+                    repos.add(repo);
+                }
+            }
+        } catch (Exception e) {
+            logger.severe("IOException while listing repositories in the organization.");
+            e.printStackTrace();
+        }
+
+        return repos;
+    }
+
     /**
      * Gets a repository by name.
      * @param name The name of the repository.

src/main/java/nl/andrewlalis/ui/control/command/executables/ListRepos.java

@@ -0,0 +1,48 @@
+package nl.andrewlalis.ui.control.command.executables;
+
+import nl.andrewlalis.git_api.GithubManager;
+import org.kohsuke.github.GHRepository;
+
+import java.util.List;
+import java.util.logging.Logger;
+
+/**
+ * This executable shows a list of repositories with a given substring.
+ */
+public class ListRepos extends GithubExecutable {
+
+
+    /**
+     * The logger for outputting debug info.
+     */
+    private static final Logger logger = Logger.getLogger(ListRepos.class.getName());
+    static {
+        logger.setParent(Logger.getGlobal());
+    }
+
+    @Override
+    protected boolean executeWithManager(GithubManager manager, String[] args) {
+        if (args.length < 1) {
+            return false;
+        }
+
+        List<GHRepository> repos = manager.listReposWithPrefix(args[0]);
+        logger.info(outputRepoList(repos));
+
+        return true;
+    }
+
+    /**
+     * Prints a nicely formatted list of repositories to a string.
+     * @param repos The list of repositories.
+     * @return A string representation of the list of repos.
+     */
+    private static String outputRepoList(List<GHRepository> repos) {
+        StringBuilder sb = new StringBuilder();
+        sb.append("List of ").append(repos.size()).append(" repositories:\n");
+        for (GHRepository repo : repos) {
+            sb.append('\t').append(repo.getName()).append('\n');
+        }
+        return sb.toString();
+    }
+}