refactor!: replace build.rs with compile-time macro build steps

BREAKING CHANGE: Replace the `build`/`builds` feature system with
compile-time macro-driven generation. `gen_program!()` now automatically
invokes `build_comp!()` and `build_pathf!()` when the `comp`/`pathf`
features are enabled, eliminating the need for `build.rs` and
`[build-dependencies]` blocks.

This removes the `build` feature, the `mingling::build` module, and all
related build-time API functions. Completion scripts are now written to
`{target_directory}/mingling/` instead of `target/release/`. The
`mingling_cli` uses `build_comp!("mling")` for its custom binary name.

2 files changed, 20 insertions, 5 deletions

diff --git a/mingling_cli/src/lib.rs b/mingling_cli/src/lib.rs
index d5a5b22..0b93f08 100644
--- a/mingling_cli/src/lib.rs
+++ b/mingling_cli/src/lib.rs
@@ -24,6 +24,10 @@ pub mod proj_mgr;
 pub mod updater;
 pub mod utils;
 
+// The `comp` feature makes `gen_program!()` generate completion scripts named after
+// the crate (`mingling-cli_comp.*`). Generate an additional set for the `mling` binary.
+mingling::macros::build_comp!("mling");
+
 #[help]
 pub fn help_global(_: EntryFallback) -> String {
     format!("{}\n", include_str!("../help/help.txt").parse_color_code())
diff --git a/mingling_cli/src/pkg_mgr/cmd_install.rs b/mingling_cli/src/pkg_mgr/cmd_install.rs
index c7dcaef..0b552a6 100644
--- a/mingling_cli/src/pkg_mgr/cmd_install.rs
+++ b/mingling_cli/src/pkg_mgr/cmd_install.rs
@@ -34,6 +34,9 @@ pub struct StateInstallBuild {
     pub workspace_root: PathBuf,
     pub install_dir: PathBuf,
     pub release_dir: PathBuf,
+    /// Directory holding Mingling's compile-time build outputs
+    /// (`{target_directory}/mingling/`), e.g. the completion scripts.
+    pub mingling_dir: PathBuf,
     pub exe_suffix: &'static str,
     pub enable: bool,
 }
@@ -43,6 +46,9 @@ pub struct StateInstallBuild {
 pub struct StateInstallCopy {
     pub install_dir: PathBuf,
     pub release_dir: PathBuf,
+    /// Directory holding Mingling's compile-time build outputs
+    /// (`{target_directory}/mingling/`), e.g. the completion scripts.
+    pub mingling_dir: PathBuf,
     pub exe_suffix: &'static str,
     pub installed: Vec<PathBuf>,
     pub enable: bool,
@@ -95,6 +101,10 @@ pub fn install(
             .target_directory
             .join("release")
             .into_std_path_buf(),
+        mingling_dir: metadata
+            .target_directory
+            .join("mingling")
+            .into_std_path_buf(),
         exe_suffix: env::consts::EXE_SUFFIX,
         enable: enable.bool(),
     }
@@ -117,6 +127,7 @@ pub fn handle_state_install_build(state: StateInstallBuild) -> Next {
     StateInstallCopy {
         install_dir: state.install_dir,
         release_dir: state.release_dir,
+        mingling_dir: state.mingling_dir,
         exe_suffix: state.exe_suffix,
         installed: vec![],
         enable: state.enable,
@@ -159,13 +170,13 @@ pub fn handle_state_install_copy(
         }
     }
 
-    // Completion scripts are generated into the build profile directory
-    // (OUT_DIR/../../../), copy every one whose name contains `_comp`,
-    // regardless of its suffix
-    for entry in fs::read_dir(&state.release_dir).map_err(|e| {
+    // Completion scripts are generated into `{target_directory}/mingling/` at
+    // compile time (via `build_comp!()`); copy every one whose name contains
+    // `_comp`, regardless of its suffix.
+    for entry in fs::read_dir(&state.mingling_dir).map_err(|e| {
         io::Error::new(
             e.kind(),
-            format!("failed to read {}: {e}", state.release_dir.display()),
+            format!("failed to read {}: {e}", state.mingling_dir.display()),
         )
     })? {
         let entry = entry.map_err(|e| {