gitindex: Add GitIndex.set_to_tree(treeish) method

This is used to set the state of the index to that of a previously known
commit. This is needed for the build without commit logic, so that
commits generated are that of the last commit in the repository and
anything uncommitted.

2 files changed, 13 insertions, 0 deletions

diff --git a/morphlib/gitindex.py b/morphlib/gitindex.py
index d8de8824..7cac2311 100644
--- a/morphlib/gitindex.py
+++ b/morphlib/gitindex.py
@@ -97,3 +97,7 @@ class GitIndex(object):
         for code, to_path, from_path in self._get_status():
             if code not in (STATUS_UNTRACKED, STATUS_IGNORED):
                 yield code, to_path, from_path
+
+    def set_to_tree(self, treeish):
+        '''Modify the index to contain the contents of the treeish.'''
+        self._run_git('read-tree', treeish)
diff --git a/morphlib/gitindex_tests.py b/morphlib/gitindex_tests.py
index db1e0e9b..2dcb5003 100644
--- a/morphlib/gitindex_tests.py
+++ b/morphlib/gitindex_tests.py
@@ -54,3 +54,12 @@ class GitIndexTests(unittest.TestCase):
         self.assertEqual(sorted(idx.get_uncommitted_changes()),
                          [('D ', 'foo', None)])
         # 'D ' means not in the index, but in the working tree
+
+    def test_set_to_tree_alt_index(self):
+        gd = morphlib.gitdir.GitDirectory(self.dirname)
+        idx = gd.get_index(os.path.join(self.tempdir, 'index'))
+        # Read the HEAD commit into the index, which is the same as the
+        # working tree, so there are no uncommitted changes reported
+        # by status
+        idx.set_to_tree(gd.HEAD)
+        self.assertEqual(list(idx.get_uncommitted_changes()),[])