Move 'git config' wrapper into its own class

We use 'git config' format config files outside Git repos, so it's
useful to have a helper class independent of the GitDirectory class.

This allows us to use it in the sysbranchdir.open() function to remove
a hack.

Change-Id: Ifa5e87f404d10666c98b9469079b7925d16becf6

3 files changed, 75 insertions, 18 deletions

diff --git a/morphlib/gitdir.py b/morphlib/gitdir.py
index 688e4b34..9cb62e3b 100644
--- a/morphlib/gitdir.py
+++ b/morphlib/gitdir.py
@@ -134,6 +134,60 @@ class PushFailureError(PushError):
                                  'stderr: %(stderr)s' % locals())
 
 
+class Config(object):
+    '''Class representing Git repo configuration.
+
+    The 'git config' format is reusable outside of Git repos, and this class
+    can be used for these files too.
+
+    This class doesn't take any notice of updates by other processes to the
+    config file, at present. Updates are cached in memory, so changes made from
+    outside the process may be ignored.
+
+    '''
+    def __init__(self, config_file, runcmd=None):
+        '''Creates a Config instance.
+
+        The 'filepath' parameter can be None if 'runcmd' is passed. Calls to
+        'git config' will be passed through 'runcmd', which can set the 'cwd'
+        parameter to a git repo.
+
+        '''
+        assert runcmd or config_file
+
+        if runcmd:
+            self.runcmd = runcmd
+            self.extra_args = []
+        else:
+            self.runcmd = cliapp.runcmd
+            self.extra_args = ['-f', config_file]
+
+        self.cache = dict()
+
+    def __setitem__(self, key, value):
+        '''Set a git repository configuration variable.
+
+        The key must have at least one period in it: foo.bar for example,
+        not just foo. The part before the first period is interpreted
+        by git as a section name.
+
+        '''
+        self.cache[key] = value
+        self.runcmd(['git', 'config'] + self.extra_args + [key, value])
+
+    def __getitem__(self, key):
+        '''Return value for a git repository configuration variable.
+
+        If the variable is unset, this will raise cliapp.AppException.
+
+        '''
+        if key not in self.cache:
+            value = self.runcmd(
+                ['git', 'config'] + self.extra_args + ['-z', key])
+            self.cache[key] = value.rstrip('\0')
+        return self.cache[key]
+
+
 class RefSpec(object):
     '''Class representing how to push or pull a ref.
 
@@ -384,7 +438,7 @@ class GitDirectory(object):
             dirname = morphlib.util.find_root(dirname, '.git')
 
         self.dirname = dirname
-        self._config = {}
+        self.config = Config(config_file=None, runcmd=self._runcmd)
 
         self._ensure_is_git_repo()
 
@@ -486,9 +540,7 @@ class GitDirectory(object):
         by git as a section name.
 
         '''
-
-        morphlib.git.gitcmd(self._runcmd, 'config', key, value)
-        self._config[key] = value
+        self.config[key] = value
 
     def get_config(self, key):
         '''Return value for a git repository configuration variable.
@@ -496,11 +548,7 @@ class GitDirectory(object):
         If the variable is unset, this will raise cliapp.AppException.
 
         '''
-
-        if key not in self._config:
-            value = morphlib.git.gitcmd(self._runcmd, 'config', '-z', key)
-            self._config[key] = value.rstrip('\0')
-        return self._config[key]
+        return self.config[key]
 
     def get_remote(self, *args, **kwargs):
         '''Get a remote for this Repository.
diff --git a/morphlib/gitdir_tests.py b/morphlib/gitdir_tests.py
index f606dfe7..0eafc0e8 100644
--- a/morphlib/gitdir_tests.py
+++ b/morphlib/gitdir_tests.py
@@ -90,6 +90,13 @@ class GitDirectoryTests(unittest.TestCase):
         gitdir.set_config('foo.bar', 'yoyo')
         self.assertEqual(gitdir.get_config('foo.bar'), 'yoyo')
 
+    def test_sets_and_gets_configuration_from_file(self):
+        gitdir = self.empty_git_directory()
+        config = morphlib.gitdir.Config(
+            config_file=os.path.join(gitdir.dirname, '.git', 'config'))
+        config['foo.bar'] = 'yoyo'
+        self.assertEqual(config['foo.bar'], 'yoyo')
+
     def test_gets_index(self):
         gitdir = self.empty_git_directory()
         self.assertIsInstance(gitdir.get_index(), morphlib.gitindex.GitIndex)
diff --git a/morphlib/sysbranchdir.py b/morphlib/sysbranchdir.py
index 69119f5b..3ca5a8cb 100644
--- a/morphlib/sysbranchdir.py
+++ b/morphlib/sysbranchdir.py
@@ -50,6 +50,8 @@ class SystemBranchDirectory(object):
         self.root_repository_url = root_repository_url
         self.system_branch_name = system_branch_name
 
+        self.config = morphlib.gitdir.Config(config_file=self._config_path)
+
     @property
     def _magic_path(self):
         return os.path.join(self.root_directory, '.morph-system-branch')
@@ -60,14 +62,11 @@ class SystemBranchDirectory(object):
 
     def set_config(self, key, value):
         '''Set a configuration key/value pair.'''
-        morphlib.git.gitcmd(cliapp.runcmd, 'config', '-f',
-                            self._config_path, key, value)
+        self.config[key] = value
 
     def get_config(self, key):
         '''Get a configuration value for a given key.'''
-        value = morphlib.git.gitcmd(cliapp.runcmd, 'config', '-f',
-                                    self._config_path, key)
-        return value.strip()
+        return self.config[key]
 
     def _find_git_directory(self, repo_url):
         for gd in self.list_git_directories():
@@ -210,6 +209,7 @@ class SystemBranchDirectory(object):
             yield m
 
 
+
 def create(root_directory, root_repository_url, system_branch_name):
     '''Create a new system branch directory on disk.
 
@@ -242,10 +242,12 @@ def create(root_directory, root_repository_url, system_branch_name):
 def open(root_directory):
     '''Open an existing system branch directory.'''
 
-    # Ugly hack follows.
-    sb = SystemBranchDirectory(root_directory, None, None)
-    root_repository_url = sb.get_config('branch.root')
-    system_branch_name = sb.get_config('branch.name')
+    config_file_path = os.path.join(
+        root_directory, '.morph-system-branch', 'config')
+    config = morphlib.gitdir.Config(config_file=config_file_path)
+
+    root_repository_url = config['branch.root']
+    system_branch_name = config['branch.name']
 
     return SystemBranchDirectory(
         root_directory, root_repository_url, system_branch_name)