Fix commit parent handling (#284)

* Fix typo

Without this fix, we don't catch the exception at the first commit (with
no parents) and we dump instead of completing the final step of the
scan.

* Fix handler more

And document why we're catching what we're catching

* Change log update

* Kickstart CI testing

Co-authored-by: Scott Bailey <scott.bailey@godaddy.com>

CHANGELOG.md

@@ -1,6 +1,12 @@
 vx.y.z - TBD
 ------------
 
+Bug fixes:
+
+* [#284](https://github.com/godaddy/tartufo/pull/284) - Fix handling of first
+  commit during local scans; an exception was raised instead of processing the
+  commit.
+
 Features:
 
 * [#270](https://github.com/godaddy/tartufo/issues/270) - When no refs/branches

tartufo/scanner.py

@@ -735,7 +735,9 @@ def chunks(self) -> Generator[types.Chunk, None, None]:
             for curr_commit in commits:
                 try:
                     prev_commit = curr_commit.parents[0]
-                except (KeyError, TypeError):
+                except (IndexError, KeyError, TypeError):
+                    # IndexError: current commit has no parents
+                    # KeyError: current commit has parents which are not local
                     # If a commit doesn't have a parent skip diff generation since it is the first commit
                     self.logger.debug(
                         "Skipping commit %s because it has no parents", curr_commit.hex