git clone: add revset alias for trunk()

CHANGELOG.md

@@ -20,6 +20,9 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
   individually instead of being passed a directory by setting
   `merge-tools.$TOOL.diff-invocation-mode="file-by-file"` in config.toml.
 
+* `jj git clone` adds the default branch of the remote as repository
+  settings for `revset-aliases."trunk()"`.`
+
 ### Fixed bugs
 
 ## [0.19.0] - 2024-07-03

cli/src/commands/git/clone.rs

@@ -24,6 +24,7 @@ use jj_lib::workspace::Workspace;
 use crate::cli_util::{CommandHelper, WorkspaceCommandHelper};
 use crate::command_error::{user_error, user_error_with_message, CommandError};
 use crate::commands::git::{map_git_error, maybe_add_gitignore};
+use crate::config::{write_config_value_to_file, ConfigNamePathBuf};
 use crate::git_util::{get_git_repo, print_git_import_stats, with_remote_git_callbacks};
 use crate::ui::Ui;
 
@@ -142,6 +143,18 @@ pub fn cmd_git_clone(
 
     let (mut workspace_command, stats) = clone_result?;
     if let Some(default_branch) = &stats.default_branch {
+        // Set repository level `trunk()` alias to the default remote branch.
+        let config_path = workspace_command.repo().repo_path().join("config.toml");
+        write_config_value_to_file(
+            &ConfigNamePathBuf::from_iter(["revset-aliases", "trunk()"]),
+            &format!("{default_branch}@{remote_name}"),
+            &config_path,
+        )?;
+        writeln!(
+            ui.status(),
+            "Setting the revset alias \"trunk()\" to \"{default_branch}@{remote_name}\""
+        )?;
+
         let default_branch_remote_ref = workspace_command
             .repo()
             .view()

cli/tests/test_git_clone.rs

@@ -64,6 +64,7 @@ fn test_git_clone() {
     insta::assert_snapshot!(stderr, @r###"
     Fetching into new repo in "$TEST_ENV/clone"
     branch: main@origin [new] tracked
+    Setting the revset alias "trunk()" to "main@origin"
     Working copy now at: uuqppmxq 1f0b881a (empty) (no description set)
     Parent commit      : mzyxwzks 9f01a0e0 main | message
     Added 1 files, modified 0 files, removed 0 files
@@ -175,6 +176,7 @@ fn test_git_clone_colocate() {
     insta::assert_snapshot!(stderr, @r###"
     Fetching into new repo in "$TEST_ENV/clone"
     branch: main@origin [new] tracked
+    Setting the revset alias "trunk()" to "main@origin"
     Working copy now at: uuqppmxq 1f0b881a (empty) (no description set)
     Parent commit      : mzyxwzks 9f01a0e0 main | message
     Added 1 files, modified 0 files, removed 0 files
@@ -332,6 +334,7 @@ fn test_git_clone_remote_default_branch() {
     Fetching into new repo in "$TEST_ENV/clone1"
     branch: feature1@origin [new] tracked
     branch: main@origin     [new] tracked
+    Setting the revset alias "trunk()" to "main@origin"
     Working copy now at: sqpuoqvx cad212e1 (empty) (no description set)
     Parent commit      : mzyxwzks 9f01a0e0 feature1 main | message
     Added 1 files, modified 0 files, removed 0 files
@@ -344,6 +347,15 @@ fn test_git_clone_remote_default_branch() {
       @origin: mzyxwzks 9f01a0e0 message
     "###);
 
+    // "trunk()" alias should be set to default branch "main"
+    let stdout = test_env.jj_cmd_success(
+        &test_env.env_root().join("clone1"),
+        &["config", "list", "--repo", "revset-aliases.'trunk()'"],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    revset-aliases.'trunk()' = "main@origin"
+    "###);
+
     // Only the default branch will be imported if auto-local-branch is off
     test_env.add_config("git.auto-local-branch = false");
     let (_stdout, stderr) =
@@ -352,7 +364,8 @@ fn test_git_clone_remote_default_branch() {
     Fetching into new repo in "$TEST_ENV/clone2"
     branch: feature1@origin [new] untracked
     branch: main@origin     [new] untracked
-    Working copy now at: pmmvwywv fa729b1e (empty) (no description set)
+    Setting the revset alias "trunk()" to "main@origin"
+    Working copy now at: rzvqmyuk cc8a5041 (empty) (no description set)
     Parent commit      : mzyxwzks 9f01a0e0 feature1@origin main | message
     Added 1 files, modified 0 files, removed 0 files
     "###);
@@ -362,6 +375,35 @@ fn test_git_clone_remote_default_branch() {
     main: mzyxwzks 9f01a0e0 message
       @origin: mzyxwzks 9f01a0e0 message
     "###);
+
+    // Change the default branch in remote
+    git_repo.set_head("refs/heads/feature1").unwrap();
+    let (_stdout, stderr) =
+        test_env.jj_cmd_ok(test_env.env_root(), &["git", "clone", "source", "clone3"]);
+    insta::assert_snapshot!(stderr, @r###"
+    Fetching into new repo in "$TEST_ENV/clone3"
+    branch: feature1@origin [new] untracked
+    branch: main@origin     [new] untracked
+    Setting the revset alias "trunk()" to "feature1@origin"
+    Working copy now at: nppvrztz b8a8a17b (empty) (no description set)
+    Parent commit      : mzyxwzks 9f01a0e0 feature1 main@origin | message
+    Added 1 files, modified 0 files, removed 0 files
+    "###);
+    insta::assert_snapshot!(
+        get_branch_output(&test_env, &test_env.env_root().join("clone2")), @r###"
+    feature1@origin: mzyxwzks 9f01a0e0 message
+    main: mzyxwzks 9f01a0e0 message
+      @origin: mzyxwzks 9f01a0e0 message
+    "###);
+
+    // "trunk()" alias should be set to new default branch "feature1"
+    let stdout = test_env.jj_cmd_success(
+        &test_env.env_root().join("clone3"),
+        &["config", "list", "--repo", "revset-aliases.'trunk()'"],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    revset-aliases.'trunk()' = "feature1@origin"
+    "###);
 }
 
 fn get_branch_output(test_env: &TestEnvironment, repo_path: &Path) -> String {

docs/revsets.md

@@ -362,6 +362,10 @@ for a comprehensive list.
   tried. If more than one potential trunk commit exists, the newest one is
   chosen. If none of the branches exist, the revset evaluates to `root()`.
 
+  When working with an existing Git repository (via `jj git clone`),
+  `trunk()` will be overridden at the repository level to the default branch of
+  the remote.
+
   You can [override](./config.md) this as appropriate. If you do, make sure it
   always resolves to exactly one commit. For example: