Let a tag's computed prefix bring its own separating space

The space between a pane's path and its commands belongs to the tag's own
text, so deleting it, or truncating the 9P tag and writing `Get`, ran the
path and the word together for Look and Exec. The prefix now adds a space
whenever the text does not start with one; every default text does, so the
default tags read and render as before.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 21 insertions, 13 deletions

diff --git a/src/tagline.zig b/src/tagline.zig
index a918689b..8bd8000a 100644
--- a/src/tagline.zig
+++ b/src/tagline.zig
@@ -104,19 +104,27 @@ pub fn revealHeader(p: *Pardes) void {
 
 pub fn tagPrefix(p: *Pardes, pane: *Pane) ![]u8 {
     const arena = p.scratch.allocator();
-    if (comptime pdf_enabled) if (pane.pdf) |pv| return std.fmt.allocPrint(
-        arena,
-        "{s} [{d}/{d}]",
-        .{ pv.path, pv.page + 1, pv.page_count },
-    );
-    if (pane.image) |*state| return panes.Image.tagPrefix(arena, state);
-    if (pane.file) |f| {
-        const name = if (pane.prompt == .name) pane.input.own orelse f.path else f.path;
-        if (panes.Output.fileTraits(f.output).saves and f.revision != f.saved_revision)
-            return std.fmt.allocPrint(arena, "{s}{s}", .{ name, dirty_marker });
-        return arena.dupe(u8, name);
-    }
-    return arena.dupe(u8, pane.cwdSlice());
+    const prefix = prefix: {
+        if (comptime pdf_enabled) if (pane.pdf) |pv|
+            break :prefix try std.fmt.allocPrint(arena, "{s} [{d}/{d}]", .{ pv.path, pv.page + 1, pv.page_count });
+        if (pane.image) |*state| break :prefix try panes.Image.tagPrefix(arena, state);
+        if (pane.file) |f| {
+            const name = if (pane.prompt == .name) pane.input.own orelse f.path else f.path;
+            if (panes.Output.fileTraits(f.output).saves and f.revision != f.saved_revision)
+                break :prefix try std.fmt.allocPrint(arena, "{s}{s}", .{ name, dirty_marker });
+            break :prefix name;
+        }
+        break :prefix pane.cwdSlice();
+    };
+    // The space between the prefix and the tag's own text is the text's
+    // (every default starts with one), but the prefix is computed, so it
+    // cannot trust the text to keep it: with it deleted, Look and Exec
+    // would see the path and the first word as one. The prefix brings its
+    // own then.
+    const tail = curTail(pane);
+    if (tail.len > 0 and std.mem.indexOfScalar(u8, " \t\n", tail[0]) == null)
+        return std.fmt.allocPrint(arena, "{s} ", .{prefix});
+    return arena.dupe(u8, prefix);
 }
 
 /// The tag's own text: what the user made of it, or until then the