Enable use of REPO_CONFIG_DIR to customize .repoconfig location

For use cases with multiple instances of repo, eg some CI environments.

Bug: https://crbug.com/gerrit/15803
Change-Id: I65c1cfc8f6a98adfeb5efefc7ac6b45bf8e134de
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/356719
Tested-by: Gavin Mak <gavinmak@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

docs/internal-fs-layout.md

@@ -243,7 +243,9 @@ The `[branch]` settings are updated by `repo start` and `git branch`.
 
 ## ~/ dotconfig layout
 
-Repo will create & maintain a few files in the user's home directory.
+Repo will create & maintain a few files under the `.repoconfig/` directory.
+This is placed in the user's home directory by default but can be changed by
+setting `REPO_CONFIG_DIR`.
 
 *   `.repoconfig/`: Repo's per-user directory for all random config files/state.
 *   `.repoconfig/config`: Per-user settings using [git-config] file format.

git_config.py

@@ -69,8 +69,6 @@ def _key(name):
 class GitConfig(object):
   _ForUser = None
 
-  _USER_CONFIG = '~/.gitconfig'
-
   _ForSystem = None
   _SYSTEM_CONFIG = '/etc/gitconfig'
 
@@ -83,9 +81,13 @@ class GitConfig(object):
   @classmethod
   def ForUser(cls):
     if cls._ForUser is None:
-      cls._ForUser = cls(configfile=os.path.expanduser(cls._USER_CONFIG))
+      cls._ForUser = cls(configfile=cls._getUserConfig())
     return cls._ForUser
 
+  @staticmethod
+  def _getUserConfig():
+    return os.path.expanduser('~/.gitconfig')
+
   @classmethod
   def ForRepository(cls, gitdir, defaults=None):
     return cls(configfile=os.path.join(gitdir, 'config'),
@@ -415,7 +417,10 @@ class GitConfig(object):
 class RepoConfig(GitConfig):
   """User settings for repo itself."""
 
-  _USER_CONFIG = '~/.repoconfig/config'
+  @staticmethod
+  def _getUserConfig():
+    repo_config_dir = os.getenv('REPO_CONFIG_DIR', os.path.expanduser('~'))
+    return os.path.join(repo_config_dir, '.repoconfig/config')
 
 
 class RefSpec(object):

repo

@@ -149,7 +149,7 @@ if not REPO_REV:
 BUG_URL = 'https://bugs.chromium.org/p/gerrit/issues/entry?template=Repo+tool+issue'
 
 # increment this whenever we make important changes to this script
-VERSION = (2, 30)
+VERSION = (2, 32)
 
 # increment this if the MAINTAINER_KEYS block is modified
 KEYRING_VERSION = (2, 3)
@@ -265,7 +265,8 @@ else:
   urllib.error = urllib2
 
 
-home_dot_repo = os.path.expanduser('~/.repoconfig')
+repo_config_dir = os.getenv('REPO_CONFIG_DIR', os.path.expanduser('~'))
+home_dot_repo = os.path.join(repo_config_dir, '.repoconfig')
 gpg_dir = os.path.join(home_dot_repo, 'gnupg')