a metric base needs the commit checked out first

Signed-off-by: vsoch <vsochat@stanford.edu>

caliper/managers/git.py

@@ -73,6 +73,9 @@ def init(self, dest=None):
     def config(self, key, value, dest=None):
         self.run_command(self.init_cmd(dest) + ["config", key, value])
 
+    def checkout(self, commit, dest=None):
+        self.run_command(self.init_cmd(dest) + ["checkout", commit])
+
     def ls_files(self, dest=None):
         """init an empty repository in a directory of choice"""
         dest = dest or self.folder or ""

caliper/metrics/base.py

@@ -25,7 +25,11 @@ def __init__(self, git=None, filename=__file__):
         self.classpath = os.path.dirname(filename)
 
     def extract(self):
+        """extract for a metric base assumes one timepoint, so we checkout the
+        commit for the user.
+        """
         for tag, index in self.iter_tags():
+            self.git.checkout(str(tag.commit), dest=self.git.folder)
             self._data[index] = self._extract(tag.commit)
 
     @property
@@ -83,6 +87,9 @@ def _extract(self, commit1, commit2):
         pass
 
     def extract(self):
+        """extract for a change metric base has two timepoints, we don't do
+        any checkout on behalf of the user.
+        """
         for tag, parent, index in self.iter_tags():
             self._data[index] = self._extract(tag.commit, parent)
 

caliper/metrics/collection/functiondb/metric.py

@@ -28,6 +28,8 @@ def _extract(self, commit):
         # Add the temporary directory to the PYTHONPATH
         sys.path.insert(0, self.git.folder)
 
+        # Checkout the right commit
+
         # Helper function to populate lookup
         def add_functions(filepath, modulepath):