clone/show: Support shallow clones

CHANGELOG.md

@@ -19,11 +19,11 @@ _When adding new entries to the changelog, please include issue/PR numbers where
     - However, new repositories are still V1 repositories unless V2 is explicitly requested, since V2 is not yet full featured.
     - Tracking issue [#72](https://github.com/koordinates/sno/issues/72)
 
-### Using Datasets V1
+#### Using Datasets V1
 
  * Unless specific action is taken, existing repositories will remain V1, and new repositories still default to V1.
 
-### Using Datasets V2
+#### Using Datasets V2
 
  * An entire repository must be either V1 or V2, so to use V2, all data must be imported as V2.
  * Data can be imported as V2 using `sno init --import=<data> --version=2` or `sno import <data> --version=2`
@@ -35,6 +35,10 @@ _When adding new entries to the changelog, please include issue/PR numbers where
  * Geometry storage format is not yet finalised.
  * Schema / meta changes cannot be committed or diffed (note: also missing from V1).
 
+### Other changes in this release
+
+ * `sno clone` now support shallow clones (`--depth N`) to avoid cloning a repo's entire history [#174](https://github.com/koordinates/sno/issues/174)
+
 ## 0.4.1
 
 ### Packaging fix:

sno/clone.py

@@ -45,32 +45,38 @@ def get_directory_from_url(url):
     default=True,
     help="Whether to report progress to stderr",
 )
+@click.option(
+    "--depth",
+    type=click.INT,
+    help="Create a shallow clone with a history truncated to the specified number of commits.",
+)
 @click.argument("url", nargs=1)
 @click.argument(
     "directory",
     type=click.Path(exists=False, file_okay=False, writable=True),
     required=False,
 )
-def clone(ctx, do_checkout, do_progress, url, directory):
+def clone(ctx, do_checkout, do_progress, depth, url, directory):
     """ Clone a repository into a new directory """
 
     repo_path = Path(directory or get_directory_from_url(url))
+    args = [
+        "git",
+        "clone",
+        "--progress" if do_progress else "--quiet",
+        "--bare",
+        "--config",
+        "remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*",
+        url,
+        str(repo_path.resolve()),
+    ]
+    if depth is not None:
+        args.append(f'--depth={depth}')
 
     try:
         # we use subprocess because it deals with credentials much better & consistently than we can do at the moment.
         # pygit2.clone_repository() works fine except for that
-        subprocess.check_call(
-            [
-                "git",
-                "clone",
-                "--progress" if do_progress else "--quiet",
-                "--bare",
-                "--config",
-                "remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*",
-                url,
-                str(repo_path.resolve()),
-            ]
-        )
+        subprocess.check_call(args)
     except subprocess.CalledProcessError as e:
         sys.exit(translate_subprocess_exit_code(e.returncode))
 

sno/show.py

@@ -42,10 +42,18 @@ def show(ctx, *, refish, output_format, json_style, **kwargs):
     # Ensures we were given a reference to a commit, and not a tree or something
     commit = CommitWithReference.resolve(repo, refish).commit
 
-    if commit.parents:
-        parent = f"{refish}^"
-    else:
+    try:
+        parents = commit.parents
+    except KeyError:
+        # one or more parents doesn't exist.
+        # This is okay if this is the first commit of a shallow clone.
+        # (how to tell?)
         parent = EMPTY_TREE_SHA
+    else:
+        if parents:
+            parent = f"{refish}^"
+        else:
+            parent = EMPTY_TREE_SHA
     patch_writer = globals()[f"patch_output_{output_format}"]
 
     return diff.diff_with_writer(

tests/test_diff.py

@@ -1401,3 +1401,15 @@ def test_show_json_format(data_archive_readonly, cli_runner):
         assert r.exit_code == 0, r
         # output is compact, no indentation
         assert '"sno.diff/v1+hexwkb": {"' in r.stdout
+
+
+def test_show_shallow_clone(data_archive_readonly, cli_runner, tmp_path, chdir):
+    # just checking you can 'show' the first commit of a shallow clone
+    with data_archive_readonly("points") as original_path:
+        clone_path = tmp_path / "shallow-clone"
+        r = cli_runner.invoke(["clone", "--depth=1", original_path, clone_path])
+        assert r.exit_code == 0, r
+
+        with chdir(clone_path):
+            r = cli_runner.invoke(["show"])
+            assert r.exit_code == 0, r