Issue #144: Branching output of zenith branch

* Add ancestor_id to pg_list->branch_list output of pageserver.
* Display branching point (LSN) for each non-root branch.
* Add tests for `zenith branch`.

test_runner/batch_others/test_zenith_cli.py

@@ -0,0 +1,49 @@
+import pytest
+import psycopg2
+import json
+
+pytest_plugins = ("fixtures.zenith_fixtures")
+
+def helper_compare_branch_list(page_server_cur, zenith_cli):
+    """
+    Compare branches list returned by CLI and directly via API.
+    Filters out branches created by other tests.
+    """
+
+    page_server_cur.execute('branch_list;')
+    branches_api = sorted(map(lambda b: b['name'], json.loads(page_server_cur.fetchone()[0])))
+    branches_api = [b for b in branches_api if b.startswith('test_cli_') or b in ('empty', 'main')]
+
+    res = zenith_cli.run(["branch"]);
+    assert(res.stderr == '')
+    branches_cli = sorted(map(lambda b: b.split(':')[-1].strip(), res.stdout.strip().split("\n")))
+    branches_cli = [b for b in branches_cli if b.startswith('test_cli_') or b in ('empty', 'main')]
+
+    assert(branches_api == branches_cli)
+
+def test_cli_branch_list(pageserver, zenith_cli):
+
+    page_server_conn = psycopg2.connect(pageserver.connstr())
+    page_server_conn.autocommit = True
+    page_server_cur = page_server_conn.cursor()
+
+    # Initial sanity check
+    helper_compare_branch_list(page_server_cur, zenith_cli)
+
+    # Create a branch for us
+    res = zenith_cli.run(["branch", "test_cli_branch_list_main", "main"]);
+    assert(res.stderr == '')
+    helper_compare_branch_list(page_server_cur, zenith_cli)
+
+    # Create a nested branch
+    res = zenith_cli.run(["branch", "test_cli_branch_list_nested", "test_cli_branch_list_main"]);
+    assert(res.stderr == '')
+    helper_compare_branch_list(page_server_cur, zenith_cli)
+
+    # Check that all new branches are visible via CLI
+    res = zenith_cli.run(["branch"]);
+    assert(res.stderr == '')
+    branches_cli = sorted(map(lambda b: b.split(':')[-1].strip(), res.stdout.strip().split("\n")))
+
+    assert('test_cli_branch_list_main' in branches_cli)
+    assert('test_cli_branch_list_nested' in branches_cli)