Better determine git directories

- Call "git-rev-parse" only once, not twice
- In case where current directory is unreadable,
the current message is:

No '.gitreview' file found in this repository.
We don't know where your gerrit is. Please manually create
a remote named gerrit and try again.

(which is not true, because .gitreview *is* present)

After this change it fails a bit better:

Cannot determine where .git directory is
The following command failed with exit code 128
    "git rev-parse --show-toplevel --git-dir"
-----------------------
fatal: Unable to read current working directory: No such
file or directory
-----------------------

Change-Id: Idbb1e68b689f226d9434db131db5d9765752a315

git-review

@@ -163,10 +163,19 @@ def latest_is_newer():
     return False
 
 
-def get_hooks_target_file():
+def git_directories():
-    top_dir = run_command('git rev-parse --git-dir')
+    """Determine (absolute git work directory path, .git subdirectory path)"""
-    hooks_dir = os.path.join(top_dir, "hooks")
+    cmd = ("git", "rev-parse", "--show-toplevel", "--git-dir")
-    return os.path.join(hooks_dir, "commit-msg")
+    out = run_command_exc(GitDirectoriesException, *cmd)
+    try:
+        return out.split()
+    except ValueError:
+        raise GitDirectoriesException(0, out, cmd, {})
+
+
+class GitDirectoriesException(CommandFailed):
+    "Cannot determine where .git directory is"
+    EXIT_CODE = 70
 
 
 class CannotInstallHook(CommandFailed):
@@ -331,18 +340,17 @@ def check_color_support():
     return _has_color
 
 
-def get_config():
+def get_config(config_file):
     """Get the configuration options set in the .gitremote file, if present."""
     """Returns a hashmap with hostname, port, project and defaultbranch."""
     """If there is no .gitremote file, default values will be used."""
     config = dict(hostname=False, port='29418', project=False,
                   defaultbranch='master', defaultremote="gerrit",
                   defaultrebase="1")
-    top_dir = run_command('git rev-parse --show-toplevel')
+
-    target_file = os.path.join(top_dir, ".gitreview")
+    if os.path.exists(config_file):
-    if os.path.exists(target_file):
         configParser = ConfigParser.ConfigParser(config)
-        configParser.read(target_file)
+        configParser.read(config_file)
         config['hostname'] = configParser.get("gerrit", "host")
         config['port'] = configParser.get("gerrit", "port")
         config['project'] = configParser.get("gerrit", "project")
@@ -799,7 +807,9 @@ to ensure proper behavior with gerrit. Thanks!
 
 def main():
 
-    config = get_config()
+    (top_dir, git_dir) = git_directories()
+    config = get_config(os.path.join(top_dir, ".gitreview"))
+    hook_file = os.path.join(git_dir, "hooks", "commit-msg")
 
     usage = "git review [OPTIONS] ... [BRANCH]"
 
@@ -931,8 +941,6 @@ def main():
         list_reviews(remote)
         return
 
-    hook_file = get_hooks_target_file()
-
     have_hook = os.path.exists(hook_file) and os.access(hook_file, os.X_OK)
 
     if not have_hook:

git-review.1

@@ -195,6 +195,8 @@ status will be returned when there are merge conflicts with the current branch.
 Possible reasons include an attempt to apply patchset from the different branch
 or code.  This exit status will also be returned if the patchset is already
 applied to the current branch.
+.It 70
+Cannot determine top level Git directory or .git subdirectory path.
 .El
 .Pp
 Exit status larger than 31 indicates problem with