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, 13 insertions, 0 deletions

diff --git a/src/ninep/pane.zig b/src/ninep/pane.zig
index 8e827fba..245e0bb4 100644
--- a/src/ninep/pane.zig
+++ b/src/ninep/pane.zig
@@ -893,6 +893,19 @@ test "truncating the tag clears its editable tail" {
     try testing.expectEqual(Status.ok, cleared.reply.status);
     try testing.expectEqualStrings("", pane.tag.own.?);
     try testing.expect(std.mem.indexOf(u8, rd(p, tag, 0, 4096).bytes, " Mine") == null);
+
+    // Written back without a leading space, the text still stands apart
+    // from the path: the computed prefix brings the separator, so Look and
+    // Exec find `Get`, not `test.txtGet`.
+    _ = wr(p, tag, "Get");
+    try testing.expectEqualStrings("Get", pane.tag.own.?);
+    const whole = rd(p, tag, 0, 4096).bytes;
+    try testing.expectEqualStrings("/test.txt Get", whole);
+    const word = config.wordBounds(whole, whole.len - "Get".len);
+    try testing.expectEqualStrings("Get", whole[word.lo..word.hi]);
+    // and the keyboard's first column of the text is the G
+    const at = tagline.tagOffsetAt(p, pane, 0, "/test.txt ".len).?;
+    try testing.expectEqual(@as(usize, 0), at.col);
 }
 
 test "name reads the file name and writing it promotes a scratch without touching its body" {