Merge branch 'ds/sparse-checkout-harden'

Merge branch 'ds/sparse-checkout-harden'

Some rough edges in the sparse-checkout feature, especially around
the cone mode, have been cleaned up.

* ds/sparse-checkout-harden:
  sparse-checkout: fix cone mode behavior mismatch
  sparse-checkout: improve docs around 'set' in cone mode
  sparse-checkout: escape all glob characters on write
  sparse-checkout: use C-style quotes in 'list' subcommand
  sparse-checkout: unquote C-style strings over --stdin
  sparse-checkout: write escaped patterns in cone mode
  sparse-checkout: properly match escaped characters
  sparse-checkout: warn on globs in cone patterns
  sparse-checkout: detect short patterns
  sparse-checkout: cone mode does not recognize "**"
  sparse-checkout: fix documentation typo for core.sparseCheckoutCone
  clone: fix --sparse option with URLs
  sparse-checkout: create leading directories
  t1091: improve here-docs
  t1091: use check_files to reduce boilerplate