sidebar: align the numbers by default

The knob landed defaulting to "prefix" on the grounds that it is what the
strip has always drawn -- but the strip is not what this is about. A sidebar
row is wider than the name on it, and `1:api` spends the first two or three
cells of every row (three or four once you have ten tabs) on a number nobody
reads until they reach for C-a 2, pushing the names in by a distance that
depends on how many tabs are open. Right-aligned, the names start where the
statuses under them start and the numbers make a column of their own.

`tab_bar_index "prefix"` is still there and unchanged, and the top strip is
unaffected either way -- it ignores the setting, having no far end to align
against.

The tests that used `1:` as the anchor for "where a tab's name starts" now
anchor on the name, which is what they were about; two new ones cover the
default and the prefix form explicitly, so neither mode is tested only by
being the default.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/config.c b/src/config.c
index 1297856..a1d8880 100644
--- a/src/config.c
+++ b/src/config.c
@@ -951,7 +951,7 @@ void config_defaults(config_t *c) {
   c->modal_scrim = 120;
   c->status_bar = true;
   c->tab_bar_side = TAB_BAR_TOP;
-  c->tab_bar_index = TAB_INDEX_PREFIX;
+  c->tab_bar_index = TAB_INDEX_RIGHT;
   /* Wide enough for " 12:a-real-name " plus a bell; narrow enough that a
    * 100-column terminal keeps a working layout beside it. */
   c->tab_bar_width = 18;
@@ -1711,8 +1711,8 @@ char *config_render(const config_t *c) {
          : c->tab_bar_side == TAB_BAR_RIGHT ? "right"
                                             : "top");
   cb_add(&b,
-         "tab_bar_index \"%s\"  // 1:name, or the number at the sidebar's far "
-         "edge\n",
+         "tab_bar_index \"%s\"  // the sidebar's number at its far edge, or "
+         "1:name\n",
          c->tab_bar_index == TAB_INDEX_RIGHT ? "right" : "prefix");
   cb_add(&b, "tab_bar_width %u      // columns a sidebar takes\n",
          c->tab_bar_width);