feat!: rename branch merge to cherry_pick (#3986)

This PR is a **breaking** rename of #3686.

merge reads like git merge w/ three-way, replay history, combine two
lines of work. That is not this API.

This call takes one additive change on a branch and lands it on main.
New column, including a blob column. Main's existing columns are not
rewritten. If it cannot land, you get `status="failed"` and
`diff.errors`, not a merge conflict to resolve.

Cherry-pick is terminology that aligns more with that.

```python
table = db.open_table("images")
table.branches.create("exp")
exp = table.branches.checkout("exp")

exp.add_columns({"tag": "cast('draft' as string)"})

diff = table.branches.diff("exp")
preview = table.branches.cherry_pick("exp", dry_run=True)
result = table.branches.cherry_pick("exp")

if result["status"] == "cherryPicked":
    print("landed at", result["mainVersionAfter"])
elif result["status"] == "failed":
    print(result["diff"]["errors"])
```

### Behavior

- Remote / Enterprise only. Local still NotSupported.
- HTTP 409 is not an exception. It is Ok with status="failed" and
diff.errors (CherryPickError).
- Unknown error / status codes still parse as Unknown.
- Requests are not retried. 409 is final and carries the body.
- Endpoint is POST /v1/table/{id}/branches/cherry_pick/.
- merge_insert and Table.merge are unchanged.

### Testing
- `cargo test -p lancedb --features remote diff_branch`
- `cargo test -p lancedb --features remote cherry_pick`
- `pytest python/python/tests/test_remote_db.py -k cherry_pick`
- node `remote.test.ts` diffs / cherry-picks path

nodejs/lancedb/index.ts

@@ -135,10 +135,10 @@ export {
   BranchColumnChange,
   BranchIndexSummary,
   BranchRowCountSummary,
-  MergeBlocker,
+  CherryPickError,
   BranchDiff,
-  MergePreview,
-  MergeBranchResult,
+  CherryPickPreview,
+  CherryPickResult,
   AddDataOptions,
   UpdateOptions,
   OptimizeOptions,

nodejs/lancedb/table.ts

@@ -1557,8 +1557,8 @@ export interface BranchRowCountSummary {
   deltaAvailable: boolean;
 }
 
-/** A reason why a branch cannot currently be merged. */
-export interface MergeBlocker {
+/** A reason why a cherry-pick cannot currently land. */
+export interface CherryPickError {
   code: string;
   message: string;
 }
@@ -1578,20 +1578,19 @@ export interface BranchDiff {
   changedColumns: BranchColumnChange[];
   addedIndexes: BranchIndexSummary[];
   removedIndexes: BranchIndexSummary[];
-  mergeable: boolean;
-  mergeBlockers: MergeBlocker[];
+  errors: CherryPickError[];
 }
 
-/** Changes that would be, or were, promoted by a branch merge. */
-export interface MergePreview {
+/** Changes that would be, or were, promoted by a cherry-pick. */
+export interface CherryPickPreview {
   promotedColumns: string[];
 }
 
-/** Result of previewing or attempting a branch merge. */
-export interface MergeBranchResult {
-  status: "ready" | "rejected" | "notImplemented" | "merged" | "unknown";
+/** Result of previewing or attempting a cherry-pick. */
+export interface CherryPickResult {
+  status: "ready" | "failed" | "notImplemented" | "cherryPicked" | "unknown";
   diff: BranchDiff;
-  preview: MergePreview;
+  preview: CherryPickPreview;
   mainVersionAfter?: number;
 }
 
@@ -1654,21 +1653,21 @@ export class Branches {
   }
 
   /**
-   * Merge a branch into main.
+   * Cherry-pick a branch onto main.
    *
-   * Set `dryRun` to `true` to preview the merge. A rejected merge resolves
-   * with `status: "rejected"` instead of throwing.
+   * Set `dryRun` to `true` to preview. A failed cherry-pick resolves
+   * with `status: "failed"` instead of throwing.
    *
-   * @param fromBranch Branch to merge from.
-   * @param dryRun When true, only preview the merge. Defaults to false.
+   * @param fromBranch Branch to cherry-pick from.
+   * @param dryRun When true, only preview. Defaults to false.
    */
-  async merge(
+  async cherryPick(
     fromBranch: string,
     dryRun: boolean = false,
-  ): Promise<MergeBranchResult> {
-    return (await this.#inner.merge(
+  ): Promise<CherryPickResult> {
+    return (await this.#inner.cherryPick(
       fromBranch,
       dryRun,
-    )) as unknown as MergeBranchResult;
+    )) as unknown as CherryPickResult;
   }
 }