feat: add explicit flag to CLI list command (#1403)

fixes: #1372 

feature: add cli flag for `pixi list` so users can filter only for
explicit packages using `--explicit` , additionally with `-x`.

---------

Co-authored-by: Tim de Jager <tdejager89@gmail.com>

docs/reference/cli.md

@@ -351,6 +351,7 @@ List project's packages. Highlighted packages are explicit dependencies.
 - `--json`: Whether to output in json format.
 - `--json-pretty`: Whether to output in pretty json format
 - `--sort-by <SORT_BY>`: Sorting strategy [default: name] [possible values: size, name, type]
+- `--explicit (-x)`: Only list the packages that are explicitly added to the [manifest file](configuration.md).
 - `--manifest-path <MANIFEST_PATH>`: The path to [manifest file](configuration.md), by default it searches for one in the parent directories.
 - `--environment (-e)`: The environment's packages to list, if non is provided the default environment's packages will be listed.
 - `--frozen`: install the environment as defined in the lock file, doesn't update `pixi.lock` if it isn't up-to-date with [manifest file](configuration.md). It can also be controlled by the `PIXI_FROZEN` environment variable (example: `PIXI_FROZEN=true`).
@@ -360,6 +361,7 @@ List project's packages. Highlighted packages are explicit dependencies.
 ```shell
 pixi list
 pixi list --json-pretty
+pixi list --explicit
 pixi list --sort-by size
 pixi list --platform win-64
 pixi list --environment cuda

src/cli/list.rs

@@ -65,6 +65,10 @@ pub struct Args {
     /// Don't install the environment for pypi solving, only update the lock-file if it can solve without installing.
     #[arg(long)]
     pub no_install: bool,
+
+    /// Only list packages that are explicitly defined in the project.
+    #[arg(short = 'x', long)]
+    pub explicit: bool,
 }
 
 fn serde_skip_is_editable(editable: &bool) -> bool {
@@ -181,6 +185,14 @@ pub async fn execute(args: Args) -> miette::Result<()> {
             .collect::<Vec<_>>();
     }
 
+    // Filter packages by explicit if needed
+    if args.explicit {
+        packages_to_output = packages_to_output
+            .into_iter()
+            .filter(|p| p.is_explicit)
+            .collect::<Vec<_>>();
+    }
+
     // Sort according to the sorting strategy
     match args.sort_by {
         SortBy::Size => {