submarine/docs/actions.md

# Actions (draft)

**Status:** [Restore](#restore) (key `x`, [D23](decisions.md)) and
[Switch branch](#switch-branch) (key `b`, [D24](decisions.md)) are implemented. [Stage pin](#stage-pin) is still a draft; its open
questions are [at the end](#open-questions).

## Principle

Offer as few actions as possible, but enough to work with submodules.
submarine shows what differs from what git records. The actions resolve such
a difference in one of two directions:

| Action | Direction | Key |
|---|---|---|
| [Restore](#restore) | The worktree follows the recorded state | `x` |
| [Stage pin](#stage-pin) | The recorded state follows the worktree | `s` |
| [Switch branch](#switch-branch) | Both: the branch tip is recorded, then restored to | `b` |

There is nothing else for now. Committing, pushing and bumping a pin to the
tip are done outside submarine. A bump is "check out the tip in the
submodule, then `s`" (or switch to the branch with `b`).

## Restore

Makes the selected repository, and everything below it, exactly what git
records. It works on any submodule and on the superproject (header
selected). Restoring the superproject gives the exact project that the
current root commit specifies, with the pins you have staged.

### Target

| Selected | Target commit | Branch |
|---|---|---|
| Superproject | `HEAD` | stays on the current branch |
| Submodule | The pin in the parent's **index** (what the UI shows as *Pinned*); with a staged pin you choose, see below | see [Branches](#branches) |
| Nested submodule, during the recursion | The gitlink in the restored parent's index | as for a submodule |

**Staged pins are kept, at every depth.** A staged pin is a decision, not
drift. Each repository's files are reset to its `HEAD`, but its staged pins
stay in its index, and the submodules below are restored to them. So a
nested submodule with a staged pin and uncommitted changes keeps the pin
and is reset to it; its changes are discarded (and listed in the question).

**Choosing the pin.** If the selected submodule has a staged pin itself, `x`
first asks which pin to restore to:

```
Restore libs/staged to  s staged pin · c committed pin (unstages it)     any other key cancels
```

- `s`: the staged pin, which stays staged.
- `c`: the committed pin (the gitlink in the parent's `HEAD`). The parent's
  index is set back to it, which is how a pin is unstaged in submarine.

The loss check then runs for the chosen pin (the two can differ: a staged
commit that exists only locally is lost by `c`, not by `s`).

Two exceptions, where a staged pin is not kept:

- **The repository moves.** If a repository is off its pin, restore checks
  out another commit; staged pins in its own index belonged to the old one.
  They are counted as a loss (`2 staged pins`), so the question appears. Its
  submodules follow the target commit's tree.
- **An added, not yet committed submodule** is no staged pin: its
  `.gitmodules` entry is reset with the other files. Its directory then
  counts as an untracked file.

### Postconditions

After a successful restore of repository R with target T:

1. **R's HEAD is T.** The index and the worktree equal T's tree, except for
   the staged pins that were kept. No modified, added, removed or conflicted
   files remain.
2. **No in-progress operation** remains in R: merge, rebase, cherry-pick,
   revert.
3. **No untracked files or directories** remain in R. This includes leftover
   directories of submodules that T no longer has (*untracked repository*).
   Ignored files are kept.
4. **Every submodule that R's index records is present and initialized**, even if
   it was never initialized, is inactive (`submodule.<name>.active`) or has
   `update = none / merge / rebase` configured. Its URL comes from T's
   `.gitmodules` (synced into the config).
5. **Each of those submodules is restored the same way**, with its gitlink
   in R's index (T's, or a kept staged pin) as its target, recursively at
   any depth.

So the subtree shows `in sync` everywhere, except for states restore does
not change: `unpushed`, behind/ahead of the ref, and `detached HEAD on pin`.

The recursion follows **T**, not the tree loaded in the UI. A submodule that
is only in T (for example, after switching branches) is initialized. A
submodule that is only on disk is deleted as an untracked directory.

### Branches

- **Superproject:** stays on its branch. The branch is not moved, since the
  target is its own `HEAD`.
- **Submodule on the pin:** if HEAD is a branch that points at the target,
  the branch stays checked out.
- **Submodule off the pin:** HEAD is detached at the target. The branch that
  was checked out is **not moved**, so its commits stay on it.

Restore never moves, creates or deletes a branch.

### What can be lost

Restore discards work. The things it can lose:

| Lost | Where it comes from |
|---|---|
| Changed files | modified, added, removed, renamed files (`changed`) |
| Untracked files | `changed` (untracked) |
| Conflicts and in-progress operations | `conflict`; merge, rebase, cherry-pick, revert state |
| Commits | A detached HEAD off the pin whose commits are on no branch, tag or remote ref (only the reflog still has them) |
| Staged pins | Staged pins in a repository that restore moves to another commit (see [Target](#target)) |
| Repositories | An untracked directory that is a repository with its **own** `.git` directory (a clone that was never added as a submodule). Its commits may exist nowhere else. A removed submodule whose git directory is absorbed into `.git/modules` loses only its worktree. Its objects stay |

Nothing else is lost. Branches, stashes, remote refs, ignored files and
absorbed submodule git directories stay.

### Confirmation

Restore asks **only if something would be lost**. Never asking is unsafe
(`git clean -ff` deletes repositories that exist nowhere else, and nothing
undoes a restore); always asking puts a question on the harmless, common
cases (`off pin`, `missing`, a staged pin) and teaches a reflexive `y`.

- **Nothing would be lost:** restore runs at once.
- **Something would be lost:** a line above the footer says what is
  discarded, summed over the whole subtree on disk:

  ```
  Restore src/app? Discards 7 changed files in 3 repositories, 2 commits on no branch, 1 untracked repository.   y restore · n cancel
  ```

  `y` runs it, any other key cancels.
- **The state can't be read** for a repository: it is counted as `n
  repositories of unknown state` and needs the same `y`.

The check reads the disk at the moment of the keypress (`RestoreLoss`), not
the loaded statuses, so loading or stale statuses don't matter. Nothing is
lost that is not in the table above; ignored files are never touched.

### Network

A restore may need objects that are not on disk: a submodule that was never
cloned (no git directory in `.git/modules`), or a target commit that was
never fetched. **Restore may clone and fetch, but only what is missing**,
non-interactively (`GIT_TERMINAL_PROMPT=0`, ssh `BatchMode`) and with a
timeout. If the commit is on no remote, restore fails with `commit … is not
available on any remote`. This is the one place besides `f` that uses the
network (decision D23).

### Running, progress and errors

- A line above the footer shows `checking …` and then `restoring …` with a
  spinner. Only one restore runs at a time; pressing `x` meanwhile flashes
  `wait for the restore of src/app to finish`. Everything else keeps working.
- A running fetch does not block a restore.
- Done: flash `restored src/app`; the app reloads the tree and all statuses,
  because the structure can have changed.
- Failure: the restore stops with git's message, shown in red above the
  footer (`restore of src/app failed: …`) until the next key. Restore is
  idempotent, so it can be run again after fixing the cause. Repositories
  that were restored before the failure stay restored.

### Implementation note

`git.Provider.Restore` (`internal/submodule/git/restore.go`) walks the
repositories itself, top-down; the children of a repository run
concurrently, bounded by the provider's semaphore. For each repository
(`T` = target) it runs, with `-c submodule.recurse=false`:

```sh
cat-file / fetch --all            # only if T is missing locally
rebase|cherry-pick|revert --quit  # whichever is in progress; --quit, not --abort: no ref moves
checkout --force --detach T       # only if HEAD is not T, so a branch is never moved
reset --hard                      # also ends a merge
update-index --cacheinfo …        # put the staged pins back (only if HEAD did not move)
clean -ffd                        # -ff: untracked repositories too; ignored files stay
submodule sync
submodule update --init --checkout --force -- <not yet initialized children>
# then every gitlink of the index (ls-files -s) is restored the same way
```

`--checkout` overrides `submodule.<name>.update`, and the explicit paths
override `submodule.<name>.active`, so no child module is skipped.

With `c` the parent's index gets the committed pin first (`update-index
--cacheinfo` in the parent).

`RestoreLoss` (`lossOf`) follows the repositories on disk: per repository
`status` (without submodules), the in-progress state files, and
`rev-list --count HEAD --not --branches --tags --remotes` if HEAD is not the
target. A directory in the untracked list is searched for `.git`
*directories* (a standalone repository); an absorbed submodule leaves only a
`.git` file and loses just its worktree.

## Switch branch

Moves the selected repository to another branch, in one step: the tip of the
branch becomes the pin, and the repository is restored to it.

### The popup

`b` opens a popup in the middle of the screen: a search line on top, below it
the branches of the selection, local ones first, then remote ones
(`origin/…`), each group with the newest tip first. Each row shows the name
(`*` marks the checked-out branch), the short SHA and the age of the tip.
The list is read from the disk; fetch (`f`) is what brings new remote
branches.

| Key | Effect |
|---|---|
| text | Filters: every word must be in the name, case-insensitive. The selection stays on its branch if it still matches |
| `↑` `↓`, `pgup` `pgdn` | Select |
| `enter` | Switch to the selected branch |
| `esc` | Close |

Mouse: a click on a branch switches to it (like `enter`), the wheel moves the
selection, a click outside the popup closes it; a click on the title, the
search line or an empty row does nothing. Everything else is ignored while the
popup is open. A header selection switches the superproject.

### Effect

For a **submodule**, with the tip `T` the list showed:

1. The parent's index records `T` as the pin (a staged pin; if `T` is the
   committed pin, the index equals `HEAD` again).
2. The submodule, and everything below it, is [restored](#restore) to `T`.
3. HEAD is put on the branch (the branch name is the local one):
   - a local branch: checked out;
   - a remote branch `origin/feat`: the local branch `feat` is created,
     tracking it; if `feat` exists at `T` it is checked out; if it exists
     **elsewhere** it is not moved and HEAD stays detached at `T`.

For the **superproject** step 1 is left out: the branch is checked out via the
restore, so its submodules follow the pins of the new commit (staged pins of
the old state are lost, and counted).

Staging comes first, so a failed restore can be repeated with `x`. If the
branch moved since the list was read (a fetch), the switch aborts with
`origin/feat moved; open the list again`; the staged SHA is always the one
shown.

### Confirmation, network, errors

As for restore: the loss is read from the disk and the question
(`Switch src/app to origin/feat? Discards …   y switch · n cancel`) appears
only if something would be lost. A submodule that is not initialized can't be
switched (`src/app is not initialized; restore it first`). Network: only what
is missing below, like restore. Lines above the footer: `checking …`,
`switching src/app to origin/feat…`; flash `switched src/app to feat` (or
`… to origin/feat (detached: local feat is elsewhere)`); failure
`switch of src/app to origin/feat failed: …`, until the next key. One
restore or switch runs at a time.

### Implementation note

`git.Provider.Switch` (`internal/submodule/git/switch.go`): verify the ref is
still `T`; `update-index --cacheinfo` in the parent; `restoreRepo` (see
restore); then `switch` / `switch -c <local> --track <remote-branch>`.
`SwitchLoss` is `lossOf` with `T` as the target. `Branches` is one
`for-each-ref`, without the `origin/HEAD` symref.

## Stage pin

Records the commit checked out in a submodule as its new pin in the
parent's index. It is the same as `git add <path>` in the parent, but only
when it is safe.

### Available when

All of:

- the selected node is a submodule, not the superproject;
- it is `off pin` (`Checkout == CheckoutDiffers`): HEAD differs from the
  pin in the parent's index;
- its worktree is **clean** (`Worktree == WorktreeClean`). Uncommitted
  changes, untracked files and conflicts count as dirty, the same rule as
  the `changed` issue. A moved nested pin counts as a change too, so nested
  submodules are staged bottom-up: first inside the submodule, then the
  submodule itself (after a commit in it, outside submarine).

Changes *inside* nested submodules don't count. Like the `changed` issue,
staging only looks at the submodule's own worktree.

### Effect

- The parent's index records the submodule's HEAD as the gitlink of its
  path. Nothing else changes: no worktree, no other index entry, no commit.
- The submodule then shows `staged` (or `●` next to an issue), and the
  `off pin` issue is gone.
- If the checkout equals the pin in the parent's `HEAD`, staging removes
  the staged pin instead (the index equals `HEAD` again).
- If the checked-out commit is not pushed, it is staged anyway. The row
  then shows `unpushed` (Danger), which is the warning.
- There is no confirmation: nothing is lost.
- Undo: restore the submodule and choose `c` (committed pin), see
  [Target](#target).

### Implementation note

```sh
# in the submodule
git rev-parse HEAD                  # must still be the SHA shown in the UI, else abort
# in the parent
git update-index --cacheinfo 160000,<sha>,<path>
```

`update-index` stages exactly the SHA that was checked, independent of the
worktree. Flash: `staged pin of src/app` on success; git's message on
failure.

## Keys and palette

Both are submodule keys (`keyMap.Submodule`), shown in the detail pane's
palette, or in the footer when the pane can't show it. Restore is always
offered: it is idempotent, and the palette is static.

| Key | Action | Pressed when not possible (flash) |
|---|---|---|
| `x` restore | Restore the selection | `this data source can't restore` (mock); `wait for the restore of … to finish` |
| `b` switch branch | [Switch branch](#switch-branch) | `this data source can't switch branches`; `wait for the restore of … to finish`; `src/app is not initialized; restore it first` |
| `s` stage pin | [Stage pin](#stage-pin), not implemented | `src/app is on its pin` / `src/app has uncommitted changes; commit or restore them first` / `the superproject has no pin` |

`R` would sit next to `r` (reload), a dangerous mix-up for a destructive
action, hence `x`.

## Testing

- Provider (`restore_test.go`), on fixtures from `scripts/make-fixture.sh`:
  a restored superproject is exact (every repository clean, `submodule status
  --recursive` without prefixes, `libs/missing` initialized), branches are
  not moved, ignored files survive, a merge and a rebase in progress end, a
  standalone clone and a removed submodule's directory are deleted, a missing
  submodule is cloned again, `update = none` and inactive submodules are
  restored, an unavailable commit is reported. The loss is empty for off pin,
  missing and unpushed submodules, counts files, nested changes, merges,
  detached commits (not those on a branch) and standalone repositories.
- UI (`internal/tui/restore_test.go`): restores at once without a loss, asks
  with one (`y` restores, anything else cancels), the mock can't restore.
- Switch: provider (`switch_test.go`): list without `origin/HEAD`, local
  first; a remote pick stages the tip and creates a tracking branch; an
  existing local branch elsewhere is not moved; a moved ref aborts; the
  superproject switch ends exact; the loss is the restore's. Picker
  (`branches_test.go`): filter, selection, scrolling. UI (`switch_test.go`):
  opens, filters, enter switches, asks with a loss, esc closes, the mock
  can't.
- By hand in tmux on a fixture, see
  [architecture.md](architecture.md#testing).

## Open questions

Decided for restore: ignored files are kept (`clean` without `-x`); a
submodule is restored to the index gitlink, so a staged pin is its target and
survives; restore may clone and fetch what is missing; the key is `x`; it
asks only if something would be lost.

Open (stage pin):

1. **Key.** `s`?
2. **Palette.** Show it always (like restore), or only while it applies?