Álvaro Tejero Cantero 1410d66ca2
🔥 Drop support for the branching preview's older databases
Branches and databases from the preview's earlier shapes are not
supported, and such branches are recreated. The earlier shapes are the
copy model, where a branch file kept its own data payload, and the
tables registered as 0150-add-file-branch-table,
0152-add-file-branch-table and 0153-add-file-pull-request-tables. This
commit removes the code that existed only for them. A fresh database
ends with the same schema as before.

- 0155-add-file-branch-table.sql loses its header about the old
  registrations, every IF NOT EXISTS, and the base_branch_revn upgrade
  and backfill. CREATE TABLE file_branch already declares the column.
- 0156 and 0157 lose every IF NOT EXISTS.
- 0158-add-file-branch-change-data-version folds into 0157, and its
  file and registration go. CREATE TABLE file_branch_change declares
  data_version NOT NULL, because both writers of the op log, a branch
  save and the squash of an update from main, stamp every row.
- need-migration-to? loses its nil case, which replayed an unstamped
  op-log row at the base's version, and the branch derive loses the
  comment that described it. Stamped rows replay as before.
- The tests for a re-run of the branch table migration and for the
  replay of an unstamped row go, with the require the first one used.

A database that holds the preview's older shapes must drop its
branching tables and the file.is_branch column, and delete the
branching steps from its migrations table, before it boots this code.
A database that ran 0157 without 0158 lacks data_version and counts as
an older shape. A database that already ran 0155 to 0158 under these
names keeps working, because a migration runs once per name.

AI-assisted-by: claude-opus-5-5
2026-10-06 10:36:55 +02:00
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