v0.2.14 : aide Nushell, themes de couleurs et cadres blancs

- Aide facon Nushell : help <cmd>, <cmd> -h/--help, help, help commands,
  help --find <texte>, help <agent> (fiche info) - sections Usage/Flags/
  Command Type/Parameters/Input-output/Examples avec couleurs
- Commande version : tableau Nushell (commit, build, rustc, theme...) + --json ;
  build.rs pour commit/branche git ; -V reste la version courte
- Themes : --theme <nom> (default, ocean, sunset, forest, dracula, mono)
  + settings.theme dans la config ; activation VT Windows pour les couleurs
- Cadres blancs Nushell partages : list, search, status, doctor, ls/ps/
  where/get et menu d autocompletion Tab encadre (colonnes name/description)

build.rs

@@ -0,0 +1,32 @@
+//! Record build metadata (git commit and branch) at compile time so the
+//! 'am version' command can display it, like Nushell's version table.
+//!
+//! When git is unavailable (e.g. building from a source tarball) the values
+//! are simply empty.
+
+use std::process::Command;
+
+fn git(args: &[&str]) -> String {
+    Command::new("git")
+        .args(args)
+        .output()
+        .ok()
+        .filter(|o| o.status.success())
+        .map(|o| String::from_utf8_lossy(&o.stdout).trim().to_string())
+        .unwrap_or_default()
+}
+
+fn main() {
+    println!("cargo:rerun-if-changed=.git/HEAD");
+    println!("cargo:rerun-if-changed=.git/refs/heads");
+    let commit = git(&["rev-parse", "HEAD"]);
+    let branch = git(&["rev-parse", "--abbrev-ref", "HEAD"]);
+    // A detached HEAD reports the literal branch name "HEAD".
+    let branch = if branch == "HEAD" {
+        String::new()
+    } else {
+        branch
+    };
+    println!("cargo:rustc-env=AM_GIT_COMMIT={commit}");
+    println!("cargo:rustc-env=AM_GIT_BRANCH={branch}");
+}