An agent shows a test fails before the fix: tcm_test's `bin` takes a kept build's name ({"tcm": "previous"}), and tcm_cli's `build` runs a command with one, on a repro's codebase with `cwd`.
`tcm builds make <entry>` builds the codebase's tcm (its package whose command is `tcm`) as it was at a history entry, and keeps it with the others to run by its id; making it again is the one kept.
`tcm --build <name> <command>` runs the command with a kept build (known-good, previous, an id, a path), as that build runs it: here, on the codebase and branch TCM_CODEBASE and TCM_BRANCH name, or with `-C <dir>` (after it or before it) on the codebase there; its exit status is the command's. `tcm builds` lists them, each with the history entry it was made from and what changed since the build before it.