feat: M6.x glob-aware schema (mcpp field) — migrate cmdline + templates + gtest

Aligns with mcpp's M6.x descriptor schema where the `mcpp` field is
optional and accepts three shapes:

  - Absent: mcpp default-looks-up <verdir>/mcpp.toml then <verdir>/*/mcpp.toml.
  - String:  glob-resolvable path to the project's mcpp.toml.
  - Table:   inline Form B descriptor (paths are globs relative to verdir).

All paths inside the descriptor are now interpreted as globs (* matches
single segment, ** any number) to robustly handle the GitHub tarball
<repo>-<tag>/ wrap layer without depending on mcpp's old "single-subdir
auto-strip" heuristic (which broke when xlings dropped unrelated
extracted artifacts in the same verdir).

Changes:
- mcpplibs.templates.lua: Form A; mcpp field removed (default lookup
  handles <verdir>/<repo>-<tag>/mcpp.toml).
- mcpplibs.cmdline.lua: Form B; sources `src/**/*.cppm` → `*/src/**/*.cppm`.
- gtest.lua: NEW. Form B descriptor for gtest 1.15.2; ships the
  amalgamated gtest-all.cc + gtest_main.cc as a static lib via:
    mcpp = {
        sources      = { "*/googletest/src/gtest-all.cc",
                         "*/googletest/src/gtest_main.cc" },
        include_dirs = { "*/googletest/include", "*/googletest" },
        targets      = { ["gtest"] = { kind = "lib" } },
    }
  This unblocks `[dev-dependencies] gtest = "1.15.2"` in user projects.

Author: Sunrisepeak

pkgs/g/gtest.lua

@@ -0,0 +1,48 @@
+-- M6.x glob-aware Form B descriptor for gtest.
+-- All paths inside `mcpp = {}` are GLOBS relative to the verdir
+-- (~/.mcpp/registry/data/xpkgs/<idx>-x-gtest/<ver>/).  `*` matches any
+-- single path segment (so it absorbs the GitHub `<repo>-<tag>/` wrap).
+
+package = {
+    spec        = "1",
+    name        = "gtest",
+    description = "Google's C++ test framework",
+    licenses    = {"BSD-3-Clause"},
+    repo        = "https://github.com/google/googletest",
+    type        = "package",
+
+    xpm = {
+        linux = {
+            ["1.15.2"] = {
+                url    = "https://github.com/google/googletest/archive/refs/tags/v1.15.2.tar.gz",
+                sha256 = "7b42b4d6ed48810c5362c265a17faebe90dc2373c885e5216439d37927f02926",
+            },
+        },
+        macosx = {
+            ["1.15.2"] = {
+                url    = "https://github.com/google/googletest/archive/refs/tags/v1.15.2.tar.gz",
+                sha256 = "7b42b4d6ed48810c5362c265a17faebe90dc2373c885e5216439d37927f02926",
+            },
+        },
+        windows = {
+            ["1.15.2"] = {
+                url    = "https://github.com/google/googletest/archive/refs/tags/v1.15.2.tar.gz",
+                sha256 = "7b42b4d6ed48810c5362c265a17faebe90dc2373c885e5216439d37927f02926",
+            },
+        },
+    },
+
+    mcpp = {
+        language     = "c++23",
+        sources      = {
+            "*/googletest/src/gtest-all.cc",
+            "*/googletest/src/gtest_main.cc",
+        },
+        include_dirs = {
+            "*/googletest/include",
+            "*/googletest",
+        },
+        targets      = { ["gtest"] = { kind = "lib" } },
+        deps         = { },
+    },
+}

pkgs/m/mcpplibs.cmdline.lua

@@ -32,11 +32,14 @@ package = {
     },
 
     -- Workaround: upstream repo has no mcpp.toml. Drop this segment when it does.
+    -- M6.x: Form B paths are globs relative to the verdir (the untouched
+    -- xlings extract dir). The leading `*/` absorbs the GitHub tarball's
+    -- `cmdline-<tag>/` wrap layer.
     mcpp = {
         language   = "c++23",
         import_std = true,
         modules    = { "mcpplibs.cmdline" },
-        sources    = { "src/**/*.cppm" },
+        sources    = { "*/src/**/*.cppm" },
         targets    = { ["cmdline"] = { kind = "lib" } },
         deps       = { },
     },

pkgs/m/mcpplibs.templates.lua

@@ -1,7 +1,8 @@
--- AUTO-GENERATED by `mcpp emit xpkg`-equivalent (manual seed).
--- Source: https://github.com/mcpp-community/templates @ v0.0.1
--- Form A descriptor: the source repo has its own mcpp.toml, so no
--- `mcpp = {}` workaround segment is needed.
+-- Form A descriptor: the source repo has its own mcpp.toml. We omit the
+-- `mcpp` field entirely — mcpp will default-look-up <verdir>/mcpp.toml
+-- and <verdir>/*/mcpp.toml, which catches the GitHub tarball's
+-- `<repo>-<tag>/mcpp.toml` layout. Add `mcpp = "<glob>"` only if the
+-- default lookup is ambiguous or wrong for your tarball.
 package = {
     spec        = "1",
     name        = "mcpplibs.templates",
@@ -30,4 +31,6 @@ package = {
             },
         },
     },
+
+    -- (no `mcpp` field — default lookup will find <verdir>/*/mcpp.toml)
 }