Support --amend in kart apply and kart meta set

CHANGELOG.md

@@ -14,6 +14,7 @@ _When adding new entries to the changelog, please include issue/PR numbers where
 - Bugfix: don't allow `kart merge` to fast-forward if the user specifies a merge message. [#705](https://github.com/koordinates/kart/issues/705)
 - `diff`, `show`, `create-patch` and `apply` now handle attached files (as could already be created using `kart commit-files`) [#583](https://github.com/koordinates/kart/issues/583)
 - `metadata.xml` is now consistently treated as an attached file, rather than as a hidden "meta item". [#583](https://github.com/koordinates/kart/issues/583)
+- `apply` and `meta set` now support `--amend` to amend an existing commit
 
 ## 0.11.5
 

kart/apply.py

@@ -246,8 +246,9 @@ def apply_patch(
     repo,
     do_commit,
     patch_file,
-    allow_empty,
     ref="HEAD",
+    allow_empty=False,
+    amend=False,
     **kwargs,
 ):
     try:
@@ -293,6 +294,9 @@ def apply_patch(
         except KeyError:
             raise NotFound(f"No such ref {ref}")
 
+    if amend and not do_commit:
+        raise click.UsageError("--no-commit and --amend are incompatible")
+
     allow_minimal_updates = bool(resolve_missing_values_from_rs)
 
     rs = repo.structure(ref)
@@ -335,9 +339,10 @@ def apply_patch(
     if do_commit:
         commit = rs.commit_diff(
             repo_diff,
-            metadata["message"],
+            metadata.get("message"),
             author=_build_signature(metadata, "author", repo),
             allow_empty=allow_empty,
+            amend=amend,
             resolve_missing_values_from_rs=resolve_missing_values_from_rs,
         )
         click.echo(f"Commit {commit.hex}")
@@ -381,6 +386,12 @@ def apply_patch(
     help="Which ref to apply the patch onto.",
     shell_complete=ref_completer,
 )
+@click.option(
+    "--amend",
+    default=False,
+    is_flag=True,
+    help="Amend the previous commit instead of adding a new commit",
+)
 @click.argument("patch_file", type=click.File("r", encoding="utf-8"))
 def apply(ctx, **kwargs):
     """

kart/meta.py

@@ -157,6 +157,12 @@ def convert(self, value, param, ctx):
     help="Use the given message as the commit message",
     type=StringFromFile(encoding="utf-8"),
 )
+@click.option(
+    "--amend",
+    default=False,
+    is_flag=True,
+    help="Amend the previous commit instead of adding a new commit",
+)
 @click.argument("dataset")
 @click.argument(
     "items",
@@ -166,7 +172,7 @@ def convert(self, value, param, ctx):
     metavar="KEY=VALUE [KEY=VALUE...]",
 )
 @click.pass_context
-def meta_set(ctx, message, dataset, items):
+def meta_set(ctx, message, amend, dataset, items):
     """
     Sets multiple meta items for a dataset, and creates a commit.
     """
@@ -177,7 +183,7 @@ def meta_set(ctx, message, dataset, items):
             "This repo doesn't support meta changes, use `kart upgrade`"
         )
 
-    if message is None:
+    if message is None and not amend:
         message = f"Update metadata for {dataset}"
 
     def _parse(key, value):
@@ -208,6 +214,7 @@ def _parse(key, value):
         do_commit=True,
         patch_file=patch_file,
         allow_empty=False,
+        amend=amend,
     )
 
 

kart/structure.py

@@ -365,6 +365,7 @@ def commit_diff(
         author=None,
         committer=None,
         allow_empty=False,
+        amend=False,
         resolve_missing_values_from_rs: Optional["RepoStructure"] = None,
     ):
         """
@@ -391,23 +392,48 @@ def commit_diff(
             if (not allow_empty) and new_tree == self.tree:
                 raise NotFound("No changes to commit", exit_code=NO_CHANGES)
 
-            L.info("Committing...")
-
             if self.ref == "HEAD":
                 parent_commit = self.repo.head_commit
             else:
                 parent_commit = self.repo.references[self.ref].peel(pygit2.Commit)
-            parents = [parent_commit.oid] if parent_commit is not None else []
 
-            # This will also update the ref (branch) to point to the new commit
+            if amend:
+                if not parent_commit:
+                    raise click.UsageError(
+                        "Cannot --amend - there is no previous commit to amend"
+                    )
+                parents = [gp.id for gp in parent_commit.parents]
+                if not message:
+                    message = parent_commit.message
+                commit_to_ref = None
+            else:
+                parents = [parent_commit.oid] if parent_commit is not None else []
+                commit_to_ref = self.ref
+
+            if not message:
+                raise click.UsageError("Aborting commit due to empty commit message.")
+
+            L.info("Committing...")
+
+            # This will also update commit_to_ref to point to the new commit, if it is not None.
             new_commit = object_builder.commit(
-                self.ref,
+                commit_to_ref,
                 author or self.repo.author_signature(),
                 committer or self.repo.committer_signature(),
                 message,
                 parents,
             )
 
+            if amend:
+                if self.ref == "HEAD" and self.repo.head_branch is None:
+                    self.repo.head.set_target(new_commit.id)
+                elif self.ref == "HEAD" and self.repo.head_branch is not None:
+                    self.repo.references[self.repo.head_branch].set_target(
+                        new_commit.id
+                    )
+                else:
+                    self.repo.references[self.ref].set_target(new_commit.id)
+
         L.info(f"Commit: {new_commit.id.hex}")
         return new_commit
 

tests/test_meta.py

@@ -122,6 +122,31 @@ def test_meta_set(data_archive, cli_runner):
         assert meta["description"]["+"] == "newdescription"
 
 
+def test_meta_set_amend(data_archive, cli_runner):
+    with data_archive("points"):
+        r = cli_runner.invoke(
+            [
+                "meta",
+                "set",
+                "nz_pa_points_topo_150k",
+                "title=newtitle",
+                "description=newdescription",
+                "--amend",
+            ]
+        )
+        assert r.exit_code == 0, r.stderr
+        r = cli_runner.invoke(["show", "-o", "json"])
+        assert r.exit_code == 0, r.stderr
+        output = json.loads(r.stdout)
+        patch_info = output.pop("kart.show/v1")
+        assert patch_info["message"] == "Improve naming on Coromandel East coast"
+        feature = output["kart.diff/v1+hexwkb"]["nz_pa_points_topo_150k"]["feature"]
+        assert len(feature) == 5
+        meta = output["kart.diff/v1+hexwkb"]["nz_pa_points_topo_150k"]["meta"]
+        assert meta["title"] == {"-": "NZ Pa Points (Topo, 1:50k)", "+": "newtitle"}
+        assert meta["description"]["+"] == "newdescription"
+
+
 def test_meta_set_custom_fields(data_archive, cli_runner):
     with data_archive("points"):
         # Make sure this works even when we have a working copy