feat: add shell completions

Cargo.toml

@@ -168,6 +168,7 @@ gix = { version = "^0.54.1", path = "gix", default-features = false }
 time = "0.3.23"
 
 clap = { version = "4.1.1", features = ["derive", "cargo"] }
+clap_complete = "4.4.3"
 prodash = { workspace = true, optional = true }
 is-terminal = { version = "0.4.0", optional = true }
 env_logger = { version = "0.10.0", default-features = false }

src/plumbing/main.rs

@@ -7,8 +7,8 @@ use std::{
     },
 };
 
-use anyhow::{Context, Result};
-use clap::Parser;
+use anyhow::{anyhow, Context, Result};
+use clap::{CommandFactory, Parser};
 use gitoxide_core as core;
 use gitoxide_core::{pack::verify, repository::PathsOrPatterns};
 use gix::bstr::{io::BufReadExt, BString};
@@ -1219,6 +1219,18 @@ pub fn main() -> Result<()> {
                 },
             ),
         },
+        Subcommands::Completions { shell, out_dir } => {
+            let mut app = Args::command();
+            let shell = shell
+                .or_else(clap_complete::Shell::from_env)
+                .ok_or_else(|| anyhow!("The shell could not be derived from the environment"))?;
+            if let Some(out_dir) = out_dir {
+                clap_complete::generate_to(shell, &mut app, env!("CARGO_PKG_NAME"), &out_dir)?;
+            } else {
+                clap_complete::generate(shell, &mut app, env!("CARGO_PKG_NAME"), &mut std::io::stdout());
+            }
+            Ok(())
+        }
     }?;
     Ok(())
 }

src/plumbing/options/mod.rs

@@ -1,5 +1,6 @@
 use std::path::PathBuf;
 
+use clap_complete::Shell;
 use gitoxide_core as core;
 use gix::bstr::BString;
 
@@ -134,6 +135,15 @@ pub enum Subcommands {
     /// Subcommands that need no git repository to run.
     #[clap(subcommand)]
     Free(free::Subcommands),
+    /// Generate shell completions to stdout or a directory.
+    #[clap(visible_alias = "generate-completions", visible_alias = "shell-completions")]
+    Completions {
+        /// The shell to generate completions for. Otherwise it's derived from the environment.
+        #[clap(long, short)]
+        shell: Option<Shell>,
+        /// The output directory in case multiple files are generated. If not provided, will write to stdout.
+        out_dir: Option<String>,
+    },
 }
 
 #[cfg(feature = "gitoxide-core-tools-archive")]