Merge pull request #3728 from dart-lang/git-ls-remote

Git ls remote
Merge pull request #3732 from ussuri/bower-semver-support

Bower: support version specs with path omitted ("1.2.3", "~1.2.3" etc.)
Merge pull request #3731 from dart-lang/git-ls-remote

Git-salt support in bower
Merge pull request #3733 from ussuri/bower-use-git-salt-for-tags

Use git-salt's tag fetching i/o GitHub API to avoid hitting API rate limit
Merge pull request #3735 from ussuri/bower-use-git-salt-for-tags

Use workaround to enable socket features used by git-salt, used by Bower
Merge pull request #3665 from dart-lang/git-status

Git status
Merge pull request #3677 from dart-lang/reenable-git-salt-flag

Re-enable git-salt behind a flag.