repos: Add KAS_GIT_SHALLOW to implement git shallow clone/fetch

docs/command-line.rst

@@ -46,6 +46,12 @@ Environment variables
 |                          | space-separated, its replacement. E.g.:          |
 |                          | "http://.*\.someurl\.io/ http://localmirror.net/"|
 +--------------------------+--------------------------------------------------+
+| ``KAS_GIT_SHALLOW``      | Perform shallow git clone/fetch using --depth=N  |
+|                          | specified by this variable. This is useful in    |
+|                          | case CI always starts with empty work directory  |
+|                          | and this directory is always discarded after the |
+|                          | CI run.                                          |
++--------------------------+--------------------------------------------------+
 | ``SSH_PRIVATE_KEY``      | Variable containing the private key that should  |
 |                          | be added to an internal ssh-agent. This key      |
 |                          | cannot be password protected. This setting is    |

kas/repos.py

@@ -478,6 +478,11 @@ def add_cmd(self):
 
     def clone_cmd(self, srcdir, createref):
         cmd = ['git', 'clone', '-q']
+
+        depth = os.environ.get('KAS_GIT_SHALLOW')
+        if depth:
+            cmd.extend(['--depth', depth])
+
         if createref:
             cmd.extend([self.effective_url, '--bare', srcdir])
         elif srcdir:
@@ -498,6 +503,11 @@ def contains_refspec_cmd(self):
 
     def fetch_cmd(self):
         cmd = ['git', 'fetch', '-q']
+
+        depth = os.environ.get('KAS_GIT_SHALLOW')
+        if depth:
+            cmd.extend(['--depth', depth])
+
         if self.tag:
             cmd.append('--tags')
 

tests/test_commands.py

@@ -28,6 +28,7 @@
 import yaml
 import pytest
 from kas import kas
+from kas.libkas import run_cmd
 from kas.libkas import TaskExecError
 
 
@@ -83,6 +84,19 @@ def test_checkout_create_refs(changedir, tmpdir):
     assert os.path.exists('kas/.git/objects/info/alternates')
 
 
+def test_checkout_shallow(changedir, tmpdir):
+    tdir = str(tmpdir / 'test_commands')
+    shutil.copytree('tests/test_commands', tdir)
+    os.chdir(tdir)
+    os.environ['KAS_GIT_SHALLOW'] = '1'
+    kas.kas(['checkout', 'test-shallow.yml'])
+    del os.environ['KAS_GIT_SHALLOW']
+    (rc, output) = run_cmd(['git', 'rev-list', '--count', 'HEAD'], cwd='kas',
+                           fail=False, liveupdate=False)
+    assert rc == 0
+    assert output.strip() == '1'
+
+
 def test_repo_includes(changedir, tmpdir):
     tdir = str(tmpdir / 'test_commands')
     shutil.copytree('tests/test_repo_includes', tdir)

tests/test_commands/test-shallow.yml

@@ -0,0 +1,9 @@
+header:
+  version: 14
+
+repos:
+  this:
+
+  kas:
+    url: https://github.com/siemens/kas.git
+    commit: master