better base check (json and human)

crates/but/src/command/legacy/base/json.rs

@@ -0,0 +1,46 @@
+//! JSON output structures for `but base` commands.
+
+use serde::Serialize;
+
+/// JSON output for `but base check`
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub(super) struct BaseCheckOutput {
+    pub base_branch: BaseBranchInfo,
+    pub upstream_commits: UpstreamInfo,
+    pub branch_statuses: Vec<BranchStatusInfo>,
+    pub up_to_date: bool,
+    pub has_worktree_conflicts: bool,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub(super) struct BaseBranchInfo {
+    pub name: String,
+    pub remote_name: String,
+    pub base_sha: String,
+    pub current_sha: String,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub(super) struct UpstreamInfo {
+    pub count: usize,
+    pub commits: Vec<UpstreamCommit>,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub(super) struct UpstreamCommit {
+    pub id: String,
+    pub description: String,
+    pub author_name: String,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub(super) struct BranchStatusInfo {
+    pub name: String,
+    pub status: String,
+    pub rebasable: Option<bool>,
+}