0.15.0

• Added g:plug_disable_credential_helper (default: 1). Set it to 0 to keep the git credential helper enabled (#1047)
• Allowed command modifiers for on-demand-loading commands, e.g. :tab Git diff (#1110) (@subnut)
• Used the job API for system() calls in GUI Vim to reduce overhead (#1325) (@jgb)
• Made on-demand loading faster
  • Used isdirectory() to check plugin directories (#1340) (@mattn)
  • Skipped BufRead for an unnamed empty buffer (#1341) (@mattn)
• Stopped loading Python and Ruby libraries when they are not needed (#1344) (@Coacher)
• Fixed PlugStatus reporting divergence when a tag is specified (#1321) (@EESchneider)
• Fixed vim-plug commands on Windows when &shell is set to PowerShell (#1326, #1331) (@tiamat18)