merge: don't open COMMIT_MSG unless we need to append conflicts
Properly report failure when expanding a packfile
checkout: fix docs formatting for the options
Merge pull request #2457 from ethomson/merge_fix

merge: don't open COMMIT_MSG unless we need to append conflicts
Merge pull request #2468 from Airbitz/pack-error-reporting

Properly report failure when expanding a packfile
Handle local file:/// paths on Windows

Windows can't handle a path like `/c:/foo`; when turning file:///
URIs into local paths, we must strip the leading slash.