git: turn git.auto-local-branch off by default

As far as I can see in the chat, there's no objection to changing the default,
and git.auto-local-branch = false is generally preferred.

docs/branches.md isn't updated as it would otherwise conflict with #2625. I
think the "Remotes" section will need a non-trivial rewrite.

#1136, #1862

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Breaking changes
 
+* `jj git fetch` no longer imports new remote branches as local branches. Set
+  `git.auto-local-branch = true` to restore the old behavior.
+
 ### New features
 
 * Information about new and resolved conflicts is now printed by every command.

cli/src/config-schema.json

@@ -223,7 +223,7 @@
                 "auto-local-branch": {
                     "type": "boolean",
                     "description": "Whether jj creates a local branch with the same name when it imports a remote-tracking branch from git. See https://github.com/martinvonz/jj/blob/main/docs/config.md#automatic-local-branch-creation",
-                    "default": true
+                    "default": false
                 },
                 "abandon-unreachable-commits": {
                     "type": "boolean",
@@ -382,4 +382,4 @@
             }
         }
     }
-}
+}

cli/tests/test_git_fetch.rs

@@ -73,6 +73,19 @@ fn get_log_output(test_env: &TestEnvironment, workspace_root: &Path) -> String {
     test_env.jj_cmd_success(workspace_root, &["log", "-T", template, "-r", "all()"])
 }
 
+#[test]
+fn test_git_fetch_with_default_config() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+    add_git_remote(&test_env, &repo_path, "origin");
+
+    test_env.jj_cmd_ok(&repo_path, &["git", "fetch"]);
+    insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @r###"
+    origin@origin: oputwtnw ffecd2d6 message
+    "###);
+}
+
 #[test]
 fn test_git_fetch_default_remote() {
     let test_env = TestEnvironment::default();

docs/config.md

@@ -499,19 +499,19 @@ conflict is considered fully resolved when there are no conflict markers left.
 
 ### Automatic local branch creation
 
-By default, when `jj` imports a new remote-tracking branch from Git, it also
-creates a local branch with the same name. In some repositories, this
-may be undesirable, e.g.:
+When `jj` imports a new remote-tracking branch from Git, it can also create a
+local branch with the same name. This feature is disabled by default because it
+may be undesirable in some repositories, e.g.:
 
 - There is a remote with a lot of historical branches that you don't
   want to be exported to the co-located Git repo.
 - There are multiple remotes with conflicting views of that branch,
   resulting in an unhelpful conflicted state.
 
-You can disable this behavior by setting `git.auto-local-branch` like so,
+You can enable this behavior by setting `git.auto-local-branch` like so,
 
 ```toml
-git.auto-local-branch = false
+git.auto-local-branch = true
 ```
 
 This setting is applied only to new remote branches. Existing remote branches

docs/design/tracking-branches.md

@@ -352,8 +352,6 @@ Note: desired behavior of `jj branch forget` is to
 
 ## Remaining issues
 
-* `git.auto_local_branch = false` by default to help Git interop?
-  * https://github.com/martinvonz/jj/issues/1862
 * https://github.com/martinvonz/jj/issues/1278 pushing to tracked remote
   * Option could be added to push to all `tracking` remotes?
 * Track remote branch locally with different name

docs/github.md

@@ -165,12 +165,14 @@ The hyphen after `your-feature` comes from the
 
 ## Working with other people's branches
 
-By default `jj git clone` and `jj git fetch` clone all active branches from
-the remote. This means that if you want to iterate or test another
-contributor's branch you can `jj new <branchname>` onto it.
+By default, `jj git clone` imports the default remote branch (which is usually
+`main` or `master`), but `jj git fetch` doesn't import new remote branches to
+local branches. This means that if you want to iterate or test another
+contributor's branch, you'll need to do `jj new <branch>@<remote>` onto it.
 
-If your remote has a large amount of old, inactive branches or this feature is
-undesirable, set `git.auto-local-branch = false` in the config file.
+If you want to import all remote branches including inactive ones, set
+`git.auto-local-branch = true` in the config file. Then you can specify a
+contributor's branch as `jj new <branch>` instead of `jj new <branch>@<remote>`.
 
 You can find more information on that setting [here][auto-branch].
 

lib/src/settings.rs

@@ -47,7 +47,7 @@ pub struct GitSettings {
 impl GitSettings {
     pub fn from_config(config: &config::Config) -> Self {
         GitSettings {
-            auto_local_branch: config.get_bool("git.auto-local-branch").unwrap_or(true),
+            auto_local_branch: config.get_bool("git.auto-local-branch").unwrap_or(false),
             abandon_unreachable_commits: config
                 .get_bool("git.abandon-unreachable-commits")
                 .unwrap_or(true),
@@ -58,7 +58,7 @@ impl GitSettings {
 impl Default for GitSettings {
     fn default() -> Self {
         GitSettings {
-            auto_local_branch: true,
+            auto_local_branch: false,
             abandon_unreachable_commits: true,
         }
     }