feat: use "craft.git" for git where possible

craft_parts/sources/git_source.py

@@ -21,12 +21,14 @@
 import subprocess
 import sys
 from pathlib import Path
-from typing import Any, ClassVar, Literal, cast
+from typing import Any, Literal, cast
 
 import pydantic
 from overrides import overrides
 from typing_extensions import Self
 
+from craft_parts.utils.git import get_git_command
+
 from . import errors
 from .base import (
     BaseSourceModel,
@@ -81,13 +83,14 @@ class GitSource(SourceHandler):
     """
 
     source_model = GitSourceModel
-    command: ClassVar[str] = "git"
 
     @classmethod
     def version(cls) -> str:
         """Get git version information."""
         return subprocess.check_output(
-            ["git", "version"], universal_newlines=True, stderr=subprocess.DEVNULL
+            [get_git_command(), "version"],
+            universal_newlines=True,
+            stderr=subprocess.DEVNULL,
         ).strip()
 
     @classmethod
@@ -118,7 +121,7 @@ def generate_version(cls, *, part_src_dir: Path | None = None) -> str:
         try:
             output = (
                 subprocess.check_output(
-                    ["git", "-C", str(part_src_dir), "describe", "--dirty"],
+                    [get_git_command(), "-C", str(part_src_dir), "describe", "--dirty"],
                     stderr=subprocess.DEVNULL,
                 )
                 .decode(encoding)
@@ -128,7 +131,14 @@ def generate_version(cls, *, part_src_dir: Path | None = None) -> str:
             # If we fall into this exception it is because the repo is not
             # tagged at all.
             proc = subprocess.Popen(  # pylint: disable=consider-using-with
-                ["git", "-C", str(part_src_dir), "describe", "--dirty", "--always"],
+                [
+                    get_git_command(),
+                    "-C",
+                    str(part_src_dir),
+                    "describe",
+                    "--dirty",
+                    "--always",
+                ],
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE,
             )
@@ -166,7 +176,7 @@ def __init__(  # pylint: disable=too-many-arguments
 
     def _fetch_origin_commit(self) -> None:
         """Fetch from origin, using source-commit if defined."""
-        command = [self.command, "-C", str(self.part_src_dir), "fetch", "origin"]
+        command = [get_git_command(), "-C", str(self.part_src_dir), "fetch", "origin"]
         if self.source_commit:
             command.append(self.source_commit)
 
@@ -175,7 +185,7 @@ def _fetch_origin_commit(self) -> None:
     def _get_current_branch(self) -> str:
         """Get current git branch."""
         command = [
-            self.command,
+            get_git_command(),
             "-C",
             str(self.part_src_dir),
             "branch",
@@ -206,7 +216,7 @@ def _pull_existing(self) -> None:
         else:
             refspec = "refs/remotes/origin/" + self._get_current_branch()
 
-        command_prefix = [self.command, "-C", str(self.part_src_dir)]
+        command_prefix = [get_git_command(), "-C", str(self.part_src_dir)]
         command = [*command_prefix, "fetch", "--prune"]
 
         if self.source_submodules is None or len(self.source_submodules) > 0:
@@ -226,7 +236,7 @@ def _pull_existing(self) -> None:
 
     def _clone_new(self) -> None:
         """Clone a git repository, using submodules, branch, and depth if defined."""
-        command = [self.command, "clone"]
+        command = [get_git_command(), "clone"]
         if self.source_submodules is None:
             command.append("--recursive")
         else:
@@ -249,7 +259,7 @@ def _clone_new(self) -> None:
         if self.source_commit:
             self._fetch_origin_commit()
             command = [
-                self.command,
+                get_git_command(),
                 "-C",
                 str(self.part_src_dir),
                 "checkout",
@@ -296,7 +306,7 @@ def _get_source_details(self) -> dict[str, str | None]:
 
         if not tag and not branch and not commit:
             commit = self._run_output(
-                ["git", "-C", str(self.part_src_dir), "rev-parse", "HEAD"]
+                [get_git_command(), "-C", str(self.part_src_dir), "rev-parse", "HEAD"]
             )
 
         return {

craft_parts/utils/git.py

@@ -0,0 +1,32 @@
+# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
+#
+# Copyright 2024 Canonical Ltd.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License version 3 as published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Helpers to use git."""
+import shutil
+from functools import cache
+
+
+@cache
+def get_git_command() -> str:
+    """Get the git command to use.
+
+    This function will prefer the "craft.git" binary if available on the system,
+    returning its full path. Otherwise, it will always return "git", without
+    checking for availability.
+    """
+    if craft_git := shutil.which("craft.git"):
+        return craft_git
+    return "git"

docs/changelog.rst

@@ -8,6 +8,8 @@ X.Y.Z (2024-MM-DD)
 - Set JAVA_HOME environment variable in Java-based plugins. The plugin will
   try to detect the latest available JDK.
 - Add an API for :ref:`registering custom source types <how_to_add_a_source_handler>`.
+- Prefer "craft.git" as the binary to handle git sources, in environments where
+  it is available.
 
 2.1.4 (2024-12-04)
 ------------------

tests/unit/utils/test_git.py

@@ -0,0 +1,38 @@
+# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
+#
+# Copyright 2024 Canonical Ltd.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License version 3 as published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+import shutil
+
+import pytest
+from craft_parts.utils.git import get_git_command
+
+
+@pytest.mark.parametrize(
+    ("which_result", "expected_command"),
+    [
+        (None, "git"),
+        ("/usr/bin/craft.git", "/usr/bin/craft.git"),
+        (
+            "/snap/snapcraft/current/libexec/snapcraft/craft.git",
+            "/snap/snapcraft/current/libexec/snapcraft/craft.git",
+        ),
+    ],
+)
+def test_get_git_command(which_result, expected_command, mocker):
+    mocker.patch.object(shutil, "which", return_value=which_result)
+    get_git_command.cache_clear()
+
+    git_command = get_git_command()
+    assert git_command == expected_command