Replace reset_repo_to_head(repo) with GitPython.

The bugfix to disambiguate filepath from ref has been merged for a long
time so it should be safe to replace the method with gitpython.

See:
https://github.com/gitpython-developers/GitPython/pull/319

Change-Id: Ic0c5253273ea47da6567047c9172adbf513c1500

tests/base.py

@@ -434,7 +434,7 @@ class FakeGerritChange(object):
                                 self.latest_patchset),
             parent)
         repo.head.reference = ref
-        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.head.reset(working_tree=True)
         repo.git.clean('-x', '-f', '-d')
 
         path = os.path.join(self.upstream_root, self.project)
@@ -462,7 +462,7 @@ class FakeGerritChange(object):
 
         r = repo.index.commit(msg)
         repo.head.reference = 'master'
-        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.head.reset(working_tree=True)
         repo.git.clean('-x', '-f', '-d')
         repo.heads['master'].checkout()
         return r
@@ -864,7 +864,7 @@ class FakeGerritChange(object):
         repo = git.Repo(path)
 
         repo.head.reference = self.branch
-        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.head.reset(working_tree=True)
         repo.git.merge('-s', 'resolve', self.patchsets[-1]['ref'])
         repo.heads[self.branch].commit = repo.head.commit
 
@@ -2424,7 +2424,7 @@ class FakeGithubPullRequest(object):
             ref.set_object('refs/tags/init')
         self.number_of_commits += 1
         repo.head.reference = ref
-        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.head.reset(working_tree=True)
         repo.git.clean('-x', '-f', '-d')
 
         if files:
@@ -2445,7 +2445,7 @@ class FakeGithubPullRequest(object):
         # each sha on a PR may have a status set on it
         self.statuses[self.head_sha] = []
         repo.head.reference = 'master'
-        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.head.reset(working_tree=True)
         repo.git.clean('-x', '-f', '-d')
         repo.heads['master'].checkout()
 
@@ -4687,7 +4687,7 @@ class ZuulTestCase(BaseTestCase):
             repo.create_tag(tag)
 
         repo.head.reference = master
-        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.head.reset(working_tree=True)
         repo.git.clean('-x', '-f', '-d')
 
     def create_branch(self, project, branch, commit_filename='README'):
@@ -4704,14 +4704,14 @@ class ZuulTestCase(BaseTestCase):
         repo.index.commit('%s commit' % branch)
 
         repo.head.reference = repo.heads['master']
-        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.head.reset(working_tree=True)
         repo.git.clean('-x', '-f', '-d')
 
     def delete_branch(self, project, branch):
         path = os.path.join(self.upstream_root, project)
         repo = git.Repo(path)
         repo.head.reference = repo.heads['master']
-        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.head.reset(working_tree=True)
         repo.delete_head(repo.heads[branch], force=True)
 
     def create_commit(self, project, files=None, head='master',
@@ -5223,7 +5223,7 @@ class ZuulTestCase(BaseTestCase):
         path = os.path.join(self.upstream_root, project)
         repo = git.Repo(path)
         repo.head.reference = branch
-        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.head.reset(working_tree=True)
         for fn, content in files.items():
             fn = os.path.join(path, fn)
             try:

zuul/merger/merger.py

@@ -36,21 +36,6 @@ from zuul.lib.logutil import get_annotated_logger
 NULL_REF = '0000000000000000000000000000000000000000'
 
 
-def reset_repo_to_head(repo):
-    # This lets us reset the repo even if there is a file in the root
-    # directory named 'HEAD'.  Currently, GitPython does not allow us
-    # to instruct it to always include the '--' to disambiguate.  This
-    # should no longer be necessary if this PR merges:
-    #   https://github.com/gitpython-developers/GitPython/pull/319
-    try:
-        repo.git.reset('--hard', 'HEAD', '--')
-    except git.GitCommandError as e:
-        # git nowadays may use 1 as status to indicate there are still unstaged
-        # modifications after the reset
-        if e.status != 1:
-            raise
-
-
 def redact_url(url):
     parsed = urlsplit(url)
     if parsed.password is None:
@@ -542,7 +527,7 @@ class Repo(object):
             # that we clean up anything that might be left over from a merge
             # while still only preparing the working copy once.
             repo.head.reference = ref
-            reset_repo_to_head(repo)
+            repo.head.reset(working_tree=True)
             repo.git.clean('-x', '-f', '-d')
             repo.git.checkout(ref)