util gc: allow specifying prune time

This only affects pruning of the operation log for now, and only
supports the string "now" for now.

cli/src/commands/util.rs

@@ -62,7 +62,18 @@ pub(crate) struct UtilCompletionArgs {
 
 /// Run backend-dependent garbage collection.
 #[derive(clap::Args, Clone, Debug)]
-pub(crate) struct UtilGcArgs {}
+pub(crate) struct UtilGcArgs {
+    /// Time threshold
+    ///
+    /// By default, only obsolete objects and operations older than 2 weeks are
+    /// pruned.
+    ///
+    /// Only the string "now" can be passed to this parameter. Support for
+    /// arbitrary absolute and relative timestamps will come in a subsequent
+    /// release.
+    #[arg(long)]
+    prune: Option<String>,
+}
 
 /// Print a ROFF (manpage)
 #[derive(clap::Args, Clone, Debug)]
@@ -108,16 +119,21 @@ fn cmd_util_completion(
 fn cmd_util_gc(
     ui: &mut Ui,
     command: &CommandHelper,
-    _args: &UtilGcArgs,
+    args: &UtilGcArgs,
 ) -> Result<(), CommandError> {
     if command.global_args().at_operation != "@" {
         return Err(user_error(
             "Cannot garbage collect from a non-head operation",
         ));
     }
+    let keep_newer = SystemTime::now()
+        - match args.prune.as_deref() {
+            None => Duration::from_secs(14 * 86400),
+            Some("now") => Duration::ZERO,
+            _ => return Err(user_error("--prune only accepts 'now'")),
+        };
     let workspace_command = command.workspace_helper(ui)?;
-    // TODO: add command argument to specify the expiration time?
-    let keep_newer = SystemTime::now() - Duration::from_secs(14 * 86400);
+
     let repo = workspace_command.repo();
     repo.op_store()
         .gc(slice::from_ref(repo.op_id()), keep_newer)?;

cli/tests/test_util_command.rs

@@ -55,4 +55,42 @@ fn test_gc_args() {
     insta::assert_snapshot!(stderr, @r###"
     Error: Cannot garbage collect from a non-head operation
     "###);
+
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["util", "gc", "--prune=foobar"]);
+    insta::assert_snapshot!(stderr, @r###"
+    Error: --prune only accepts 'now'
+    "###);
+}
+
+#[test]
+fn test_gc_operation_log() {
+    let test_env = TestEnvironment::default();
+    // Use the local backend because GitBackend::gc() depends on the git CLI.
+    test_env.jj_cmd_ok(
+        test_env.env_root(),
+        &["init", "repo", "--config-toml=ui.allow-init-native=true"],
+    );
+    let repo_path = test_env.env_root().join("repo");
+
+    // Create an operation.
+    std::fs::write(repo_path.join("file"), "a change\n").unwrap();
+    test_env.jj_cmd_ok(&repo_path, &["commit", "-m", "a change"]);
+    let op_to_remove = test_env.current_operation_id(&repo_path);
+
+    // Make another operation the head.
+    std::fs::write(repo_path.join("file"), "another change\n").unwrap();
+    test_env.jj_cmd_ok(&repo_path, &["commit", "-m", "another change"]);
+
+    // This works before the operation is removed.
+    test_env.jj_cmd_ok(&repo_path, &["debug", "operation", &op_to_remove]);
+
+    // Remove some operations.
+    test_env.jj_cmd_ok(&repo_path, &["operation", "abandon", "..@-"]);
+    test_env.jj_cmd_ok(&repo_path, &["util", "gc", "--prune=now"]);
+
+    // Now this doesn't work.
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["debug", "operation", &op_to_remove]);
+    insta::assert_snapshot!(stderr, @r###"
+    Error: No operation ID matching "35688918195690874cbf1f282140cda33c882e48a84dbb0f92c262b52ace4a5753777432b18e9de01bc23121b23261eb2c828622836b9ec7ded7c0ca3c7c1670"
+    "###);
 }