Fix loading short layouts and custom config dirs (#4640)

* test(e2e): Write a regression test to validate behavior

w.r.t. loading and determining the session layout file. Compared to
release v0.43.1, right now there is a problem where `zellij --layout
NAME`, with `NAME` being the filename of a layout in the
`$ZELLIJ_DATA_DIR/layouts/` subfolder, doesn't resolve to the correct
layout file. Instead, zellij will silently fall back to its default
config. It does, however, recognize nonexistent configuration files.

* fix(utils): Treat bare layout names as file paths first

before defaulting to builtin layout names. This restores the behavior
shown by zellij up until 0.43.1, which was altered in a recent extension
of the server-client API.

* fix: Forward client layout information to startup code

and ensure it isn't ignored along the way. Update a bunch of tests to
react to the new function interface and write new tests to catch
deviations in the future.

* test: Fix misconfigured e2e test

to ensure that a custom `--config-dir` is indeed respected during
application startup.

* test: Rewrite config dir test to not use variable metadata

since the `LayoutInfo` object previously dumped into the snapshot
contains information that isn't platform agnostic, including an absolute
file path and a timestamp.

* docs(CHANGELOG): Mention PR #4640

in the list of changes for the next release.

* fix: Handle bare layouts with name "default" correctly

and assume a "default" layout if no layout name is given during layout
resolution. "default" may not always be the builtin default layout,
since users can write their own "default.kdl" that takes effect when
placed in the layout directory an no other layouts are explicitly
specified.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/tests/fixtures/config-dirs/e2e-upside-down/layouts/upside-down.kdl b/src/tests/fixtures/config-dirs/e2e-upside-down/layouts/upside-down.kdl
new file mode 100644
index 00000000..e682ce83
--- /dev/null
+++ b/src/tests/fixtures/config-dirs/e2e-upside-down/layouts/upside-down.kdl
@@ -0,0 +1,13 @@
+layout {
+    pane size=2 borderless=true {
+        plugin location="status-bar" {
+            classic true
+        }
+    }
+    pane focus=true
+    pane size=1 borderless=true {
+        plugin location="tab-bar" {
+            hide_swap_layout_indication true
+        }
+    }
+}