Merge branch 'cc/apply-introduce-state'

Merge branch 'cc/apply-introduce-state'

The "git apply" standalone program is being libified; this is the
first step to move many state variables into a structure that can
be explicitly (re)initialized to make the machinery callable more
than once.

The next step that moves some remaining state variables into the
structure and turns die()s into an error return that propagates up
to the caller is not queued yet but in flight.  It would be good to
review the above first and give the remainder of the series a solid
base to build on.

* cc/apply-introduce-state: (50 commits)
  builtin/apply: remove misleading comment on lock_file field
  builtin/apply: move 'newfd' global into 'struct apply_state'
  builtin/apply: add 'lock_file' pointer into 'struct apply_state'
  builtin/apply: move applying patches into apply_all_patches()
  builtin/apply: move 'state' check into check_apply_state()
  builtin/apply: move 'symlink_changes' global into 'struct apply_state'
  builtin/apply: move 'fn_table' global into 'struct apply_state'
  builtin/apply: move 'state_linenr' global into 'struct apply_state'
  builtin/apply: move 'max_change' and 'max_len' into 'struct apply_state'
  builtin/apply: move 'ws_ignore_action' into 'struct apply_state'
  builtin/apply: move 'ws_error_action' into 'struct apply_state'
  builtin/apply: move 'applied_after_fixing_ws' into 'struct apply_state'
  builtin/apply: move 'squelch_whitespace_errors' into 'struct apply_state'
  builtin/apply: remove whitespace_option arg from set_default_whitespace_mode()
  builtin/apply: move 'whitespace_option' into 'struct apply_state'
  builtin/apply: move 'whitespace_error' global into 'struct apply_state'
  builtin/apply: move 'root' global into 'struct apply_state'
  builtin/apply: move 'p_value_known' global into 'struct apply_state'
  builtin/apply: move 'p_value' global into 'struct apply_state'
  builtin/apply: move 'has_include' global into 'struct apply_state'
  ...