add an error message for cloning private repos
Upgrade to Polymer 0.10.0-pre.11
Merge pull request #1981 from ussuri/upgrade-to-polymer-0.10.0-pre.11

Upgrade to Polymer 0.10.0-pre.11
Remember repoUrl if append .git to it.
Merge pull request #1982 from dart-lang/git_rem_repo

Remember repoUrl if append .git to it.
Fix null check in git commit.
Merge pull request #1988 from dart-lang/fix_commit_null

Fix null check in git commit.
nit
Merge pull request #1979 from devoncarew/devoncarew_clone_private

add an error message for cloning private repos
Merge branch 'master' into devoncarew_handle_analysis_errors