complete rewrite in zig...

upon release v5.0 I introduced a regression through my caching system in
which I naively thought that the mtime of a directory was updated by
child directories when it actually only updates for child files.

This rewrite introduces a new caching system where instead of relying on
mtime of the index file I simply store the path to, at most, 10
untracked paths and check those before anything else. This results in
slower, but more reliable caching. However due to Zig's ease of use I
was able to bring down the overall use when statically linked to libgit2
so overall XD should be faster \o/.

I also added a visor? (O) to represent an in progress rebase.

build.zig.zon

@@ -0,0 +1,19 @@
+.{
+    .name = .XD,
+    .version = "6.0.0",
+    .fingerprint = 0x420a402a481c77c1, // Changing this has security and trust implications.
+    .minimum_zig_version = "0.15.2",
+    .dependencies = .{
+        .libgit2 = .{
+            .url = "git+https://github.com/allyourcodebase/libgit2#58dfd002d47a8c9fbd99d4a939cb343172590e1b",
+            .hash = "libgit2-1.9.0-uizqTQnZAADyPOmBklxzj_lrnfJoRLRDBbbTvi28SrZX",
+        },
+    },
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        "LICENSE",
+        "README.md",
+    },
+}