feat: add flag to limit search time

Signed-off-by: tjh <did:plc:65gha4t3avpfpzmvpbwovss7>

Cargo.toml

···
 gix = { version = "0.73.0", default-features = false, features = ["max-performance"] }
 time = { version = "0.3.41", features = ["formatting"] }
 
+[features]
+time-budget = []
+
 [profile.release]
 strip = true
 lto = "fat"

src/cli.rs

···
     #[arg(long, short = 'R', value_hint = ValueHint::DirPath, default_value = ".")]
     pub repository: PathBuf,
 
+    /// Maximum search time in milliseconds.
+    #[cfg(feature = "time-budget")]
+    #[arg(long, default_value_t = u64::MAX)]
+    pub time_limit: u64,
+
     pub subtree: Option<PathBuf>,
 }

src/main.rs

···
 use gix::traverse::commit::simple::CommitTimeOrder;
 use std::collections::HashSet;
 
+#[cfg(feature = "time-budget")]
+use std::time::Duration;
+#[cfg(feature = "time-budget")]
+use std::time::Instant;
+
 mod cli;
 
 fn main() -> anyhow::Result<()> {
     let arguments = cli::parse();
+
+    #[cfg(feature = "time-budget")]
+    let (time_limit, start) = (Duration::from_millis(arguments.time_limit), Instant::now());
+
     let repository = gix::open(arguments.repository)?;
 
     let mut current_commit = repository.resolve_revspec(&arguments.from)?;
···
 
     for revision in rev_walk.all()? {
         if interested.is_empty() {
+            break;
+        }
+
+        #[cfg(feature = "time-budget")]
+        if start.elapsed() > time_limit {
             break;
         }