feat(sync): add --reparent option

Allows `sync` to reparent commits onto the main branch, effectively "undoing"
intermediate main branch commits that would otherwise be between the original
parent and the new parent.

Author: bryango

git-branchless/src/commands/sync.rs

@@ -76,7 +76,7 @@ pub fn sync(
         resolve_merge_conflicts,
         dump_rebase_constraints,
         dump_rebase_plan,
-        reparent: _, // not yet implemented
+        reparent,
     } = *move_options;
     let build_options = BuildRebasePlanOptions {
         force_rewrite_public_commits,
@@ -111,6 +111,7 @@ pub fn sync(
             git_run_info,
             &repo,
             &event_log_db,
+            reparent,
             &build_options,
             &execute_options,
             &thread_pool,
@@ -126,6 +127,7 @@ pub fn sync(
         git_run_info,
         &repo,
         &event_log_db,
+        reparent,
         build_options,
         &execute_options,
         &thread_pool,
@@ -140,6 +142,7 @@ fn execute_main_branch_sync_plan(
     git_run_info: &GitRunInfo,
     repo: &Repo,
     event_log_db: &EventLogDb,
+    reparent: bool,
     build_options: &BuildRebasePlanOptions,
     execute_options: &ExecuteRebasePlanOptions,
     thread_pool: &ThreadPool,
@@ -275,6 +278,9 @@ fn execute_main_branch_sync_plan(
         Err(_) => return Ok(Ok(())),
     };
     builder.move_subtree(root_commit_oid, vec![upstream_main_branch_oid])?;
+    if reparent {
+        builder.reparent_subtree(root_commit_oid, vec![upstream_main_branch_oid], repo)?;
+    }
     let rebase_plan = match builder.build(effects, thread_pool, repo_pool)? {
         Ok(rebase_plan) => rebase_plan,
         Err(err) => {
@@ -302,6 +308,7 @@ fn execute_sync_plans(
     git_run_info: &GitRunInfo,
     repo: &Repo,
     event_log_db: &EventLogDb,
+    reparent: bool,
     build_options: BuildRebasePlanOptions,
     execute_options: &ExecuteRebasePlanOptions,
     thread_pool: &ThreadPool,
@@ -365,6 +372,13 @@ fn execute_sync_plans(
                     }
 
                     builder.move_subtree(root_commit.get_oid(), vec![main_branch_oid])?;
+                    if reparent {
+                        builder.reparent_subtree(
+                            root_commit.get_oid(),
+                            vec![main_branch_oid],
+                            &repo,
+                        )?;
+                    }
                     let rebase_plan = builder.build(effects, thread_pool, repo_pool)?;
                     Ok(rebase_plan.map(|rebase_plan| (root_commit_oid, rebase_plan)))
                 },

git-branchless/tests/test_sync.rs

@@ -192,6 +192,108 @@ fn test_sync_pull() -> eyre::Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_sync_reparent() -> eyre::Result<()> {
+    let git = make_git()?;
+
+    if !git.supports_reference_transactions()? {
+        return Ok(());
+    }
+    git.init_repo()?;
+
+    git.detach_head()?;
+    git.commit_file("test1", 1)?;
+    git.commit_file("test2", 2)?;
+
+    git.run(&["checkout", "master"])?;
+    git.commit_file("test3", 3)?;
+
+    git.detach_head()?;
+    git.commit_file("test4", 4)?;
+
+    git.run(&["checkout", "master"])?;
+    git.commit_file("test5", 5)?;
+
+    {
+        let stdout = git.smartlog()?;
+        insta::assert_snapshot!(stdout, @r###"
+        O f777ecc create initial.txt
+        |\
+        | o 62fc20d create test1.txt
+        | |
+        | o 96d1c37 create test2.txt
+        |
+        O 98b9119 create test3.txt
+        |\
+        | o 2b633ed create test4.txt
+        |
+        @ 117e086 (> master) create test5.txt
+        "###);
+    }
+
+    {
+        let (stdout, stderr) = git.branchless("sync", &["--reparent"])?;
+        insta::assert_snapshot!(stderr, @r###"
+        branchless: creating working copy snapshot
+        Switched to branch 'master'
+        branchless: processing checkout
+        branchless: creating working copy snapshot
+        Switched to branch 'master'
+        branchless: processing checkout
+        "###);
+        insta::assert_snapshot!(stdout, @r"
+        Attempting rebase in-memory...
+        [1/2] Committed as: 9343a7d create test1.txt
+        [2/2] Committed as: e14bee9 create test2.txt
+        branchless: processing 2 rewritten commits
+        branchless: running command: <git-executable> checkout master
+        In-memory rebase succeeded.
+        Attempting rebase in-memory...
+        [1/1] Committed as: e8f8c47 create test4.txt
+        branchless: processing 1 rewritten commit
+        branchless: running command: <git-executable> checkout master
+        In-memory rebase succeeded.
+        Synced 62fc20d create test1.txt
+        Synced 2b633ed create test4.txt
+        ");
+    }
+
+    {
+        let stdout = git.smartlog()?;
+        insta::assert_snapshot!(stdout, @r"
+        :
+        @ 117e086 (> master) create test5.txt
+        |\
+        | o 9343a7d create test1.txt
+        | |
+        | o e14bee9 create test2.txt
+        |
+        o e8f8c47 create test4.txt
+        ");
+    }
+
+    {
+        // the reparented test1 will effectively undo test3 & test5
+        let (stdout, _stderr) = git.run(&["show", "--pretty=format:", "--stat", "9343a7d"])?;
+        insta::assert_snapshot!(&stdout, @r"
+        test1.txt | 1 +
+        test3.txt | 1 -
+        test5.txt | 1 -
+        3 files changed, 1 insertion(+), 2 deletions(-)
+        ");
+
+        // similar the reparented test4 will effectively undo test5
+        let (stdout, _stderr) = git.run(&["show", "--pretty=format:", "--stat", "e8f8c47"])?;
+        insta::assert_snapshot!(&stdout, @r"
+        test4.txt | 1 +
+        test5.txt | 1 -
+        2 files changed, 1 insertion(+), 1 deletion(-)
+        ");
+    }
+
+    Ok(())
+}
+
 #[test]
 fn test_sync_stack_from_commit() -> eyre::Result<()> {
     let git = make_git()?;