Function check_changes

src/watcher/watcher.c:1247–1294

Check if a project has changes. Returns true if reindex needed. * Must NOT mutate the committed baselines (last_head, last_dirty_sig): * poll_project commits them only after a SUCCESSFUL reindex so that * busy-skips and failed runs retry instead of silently losing the change * (#937). Observations are staged in the pending_* fields. */

 * busy-skips and failed runs retry instead of silently losing the change
 * (#937). Observations are staged in the pending_* fields. */
static bool check_changes(cbm_watcher_t *w, project_state_t *s, bool *changed_out) {
    if (!changed_out) {
        return false;
    }
    *changed_out = false;
    if (!s->is_git) {
        return true;
    }

    bool changed = false;

    /* Check HEAD movement (commit, checkout, pull) */
    s->pending_head[0] = '\0';
    char head[CBM_SZ_128] = {0};
    watcher_git_status_t head_status = git_head(w, s, head, sizeof(head));
    if (head_status == WATCHER_GIT_OK) {
        if (s->last_head[0] == '\0') {
            /* First observed HEAD: adopt as baseline, not a change. */
            snprintf(s->last_head, sizeof(s->last_head), "%s", head);
        } else if (strcmp(head, s->last_head) != 0) {
            changed = true;
        }
        snprintf(s->pending_head, sizeof(s->pending_head), "%s", head);
    } else if (head_status != WATCHER_GIT_COMMAND_FAILED) {
        return false;
    }

    /* Working tree: reindex only when the DIRTY STATE ITSELF changed —
     * a persistently dirty tree polled while idle must not re-trigger
     * full reindex/write cycles (#937 write amplification). */
    uint64_t sig = 0;
    watcher_git_status_t signature_status = git_dirty_signature(w, s, &sig);
    if (signature_status == WATCHER_GIT_COMMAND_FAILED) {
        /* The repository may have been removed between baseline and poll.
         * Preserve committed observations and wait for a later clean probe. */
        return true;
    }
    if (signature_status != WATCHER_GIT_OK) {
        return false;
    }
    if (sig != s->last_dirty_sig) {
        changed = true;
    }
    s->pending_dirty_sig = sig;

    *changed_out = changed;
    return true;
}

/* Context for poll_once foreach callback */
typedef struct {