submarine/docs/requirements.md

Requirements

Problem

In repositories with many submodules, git submodule status shows pinned commit hashes. It doesn't answer the questions users actually have:

• Which branch is this submodule on, and is the pin current?
• Which submodules need my attention, and which are fine?
• Is anything dangerous, e.g. a pin that other people can't fetch?

Goals

• Show only submodules (not files), recursively nested, as a tree.
• Describe pins as ref + distance instead of a commit hash.
• Let problems stand out and keep healthy submodules quiet.
• Work comfortably with dozens to hundreds of submodules.

Functional requirements

Tree

• F1 Show all submodules of the superproject, including nested submodules of submodules, at any depth.
• F2 Group submodules by the directory of their path relative to the parent repository. A directory with submodules is shown as a non-selectable header line (e.g. src/, modules/). Submodules at the repository root have no header.
• F3 Nested submodules are shown under their parent submodule. A directory header inside a submodule (e.g. modules/) means the nested submodule lives in that subdirectory of the parent.
• F4 On startup only the first level is shown; every submodule with nested submodules is collapsed.
• F5 A collapsed submodule shows the number of its direct children, e.g. [2].
• F6 A collapsed submodule shows the number of issues hidden in all its descendants (·2), colored by the most severe hidden issue.
• F7 Expansion state of descendants is remembered when a parent is collapsed and restored when it is expanded again (except after "collapse all", which resets it).

State per submodule

• F10 Each submodule shows at most one state word: the most severe issue, plus +n if there are more. Submodules without issues show no word. See state-model.md for the full rules.
• F11 Each submodule shows its pin as a ref (origin/main, a tag, or a short SHA as a fallback) and the distance to that ref (↑n, ↓n, ↑n↓m).
• F12 A pin that is not reachable from any remote ref ("unpushed") is the most prominent state.
• F13 States load asynchronously per submodule; a submodule shows a spinner until its state is known. Loading errors are shown as error.

Detail pane

• F20 Shows the selected submodule: full path, name, all issues in words, staged-pin and detached-HEAD notes.
• F21 Shows the resolved ref, how it was resolved, and three commits: Pinned, Checkout and Tip (SHA + subject). A checkout that differs from the pin is highlighted.
• F22 Lists the commits between pin and tip (SHA, subject, author, age) with a title stating ahead/behind/diverged.
• F23 Shows child count, issues below, and the remote URL.

Header and footer

• F30 The header shows the superproject path, its branch and ahead/behind, the number of submodules, a count per issue kind (most severe first), staged pins, how many are still loading, and the time since the last fetch.
• F31 The footer shows key hints; ? toggles the full help. It temporarily shows short messages (e.g. "not implemented").

Navigation

• F40 Keyboard navigation as specified in ux-guide.md.
• F41 Mouse: click a row to select it, click ▸/▾ to toggle, scroll wheel moves the selection.

Actions (planned, not implemented)

Key	Action
u	Check out the pinned commit (git submodule update)
b	Bump the pin to the tip of its ref
f	Fetch remotes
/	Filter by name/path
!	Show only submodules with issues

Non-functional requirements

• N1 Startup must not block on the network. The tool works from local refs and shows how old they are ("fetched 2m ago"); fetching is explicit.
• N2 Loading many submodules must not freeze the UI (async, per submodule).
• N3 Colors follow the user's terminal theme (ANSI 16 colors); the UI works on dark and light backgrounds.
• N4 Meaning never depends on color alone: every state has a word.
• N5 Works without a Nerd Font. SUBMARINE_ASCII=1 replaces the few remaining Unicode symbols with ASCII.
• N6 Works in narrow terminals (detail pane hides below 90 columns).
• N7 The UI is independent of the data source: replacing the mock provider with a git provider requires no UI changes.