[PATCH v4 00/10] sparse-checkout: make set subsume init

As described at [1], the split of init and set subcommands in sparse-checkout causes multiple issues:

 * Poor performance (deleting all tracked files, then later restoring many
   and maybe even most of them)
 * Poor UI (multiple progress bars in wrappers that hide both commands under
   1 user-facing command)
 * Loss of ignored files under directories the user wanted to keep

This series fixes this bug by providing a single command to switch to a sparse-checkout: set. It does so by making set able to do the combined work of init and set. It keeps init as-is to give folks time to adapt, but marks it as deprecated. It also makes reapply able to toggle cone/non-cone mode and sparse-index/non-sparse-index mode.

Changes since v3:

 * Do not make git sparse-checkout disable throw an error when not in a
   sparse-checkout -- and document why we don't exit early either.

Changes since v2:

 * Small documentation wording improvement
 * Added Reviewed-by's from Stolee and Victoria

Changes since v1:

 * Inserted new patches 3 & 4 as additional preparatory cleanups
 * Took the new mode-toggling work code in sparse_checkout_set from the
   previous series and moved it into a new function, as a preparatory patch,
   and made it usable by init/set/reapply
 * Also updated reapply to allow mode-toggling
 * Updated the documentation as per above
 * Various other small items from review comments

A quick overview:

 * Patches 1-4: small preparatory refactorings
 * Patch 5: patch adding new function for toggling {cone,sparse-checkout}
   modes
 * Patch 6: the crux of the series; make set able to handle both init and
   set options
 * Patch 7: make reapply also able to do mode toggling
 * Patches 8-9: documentation modifications (Patch 4 is worth reviewing; it
   marks init as deprecated -- are others okay with that?)
 * Patch 10: trivial modification of git clone --sparse to use git
   sparse-checkout set rather than git sparse-checkout init.

[1] https://lore.kernel.org/git/CABPp-BE8TJ8QGAQWsSGT7S+9Xp-XmApcC9PSw3K=RQOP0rt+PQ@mail.gmail.com/

Elijah Newren (10):
  sparse-checkout: pass use_stdin as a parameter instead of as a global
  sparse-checkout: break apart functions for sparse_checkout_(set|add)
  sparse-checkout: add sanity-checks on initial sparsity state
  sparse-checkout: disallow --no-stdin as an argument to set
  sparse-checkout: split out code for tweaking settings config
  sparse-checkout: enable `set` to initialize sparse-checkout mode
  sparse-checkout: enable reapply to take --[no-]{cone,sparse-index}
  git-sparse-checkout.txt: update to document init/set/reapply changes
  Documentation: clarify/correct a few sparsity related statements
  clone: avoid using deprecated `sparse-checkout init`

 Documentation/git-clone.txt           |   8 +-
 Documentation/git-sparse-checkout.txt | 100 +++++++------
 builtin/clone.c                       |   2 +-
 builtin/sparse-checkout.c             | 204 ++++++++++++++++++++------
 t/t1091-sparse-checkout-builtin.sh    |  10 +-
 5 files changed, 227 insertions(+), 97 deletions(-)

base-commit: abe6bb3905392d5eb6b01fa6e54d7e784e0522aa
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1151%2Fnewren%2Fsparse-checkout-no-init-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1151/newren/sparse-checkout-no-init-v4
Pull-Request: https://github.com/git/git/pull/1151

Range-diff vs v3:

  1:  814aed2d125 =  1:  814aed2d125 sparse-checkout: pass use_stdin as a parameter instead of as a global
  2:  04cd57592e9 =  2:  04cd57592e9 sparse-checkout: break apart functions for sparse_checkout_(set|add)
  3:  f3af5edb25d !  3:  a8fdda35b91 sparse-checkout: add sanity-checks on initial sparsity state
     @@ Metadata
       ## Commit message ##
          sparse-checkout: add sanity-checks on initial sparsity state
      
     -    Most sparse-checkout subcommands (list, add, reapply, disable)
     -    only make sense when already in a sparse state.  Add a quick check
     -    that will error out early if this is not the case.
     +    Most sparse-checkout subcommands (list, add, reapply) only make sense
     +    when already in a sparse state.  Add a quick check that will error out
     +    early if this is not the case.
     +
     +    Also document with a comment why we do not exit early in `disable` even
     +    when core.sparseCheckout starts as false.
      
          Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
          Reviewed-by: Victoria Dye <vdye@github.com>
     @@ builtin/sparse-checkout.c: static int sparse_checkout_disable(int argc, const ch
       	struct pattern_list pl;
       	struct strbuf match_all = STRBUF_INIT;
       
     -+	if (!core_apply_sparse_checkout)
     -+		die(_("no active sparse-checkout to disable"));
     ++	/*
     ++	 * We do not exit early if !core_apply_sparse_checkout; due to the
     ++	 * ability for users to manually muck things up between
     ++	 *   direct editing of .git/info/sparse-checkout
     ++	 *   running read-tree -m u HEAD or update-index --skip-worktree
     ++	 *   direct toggling of config options
     ++	 * users might end up with an index with SKIP_WORKTREE bit set on
     ++	 * some files and not know how to undo it.  So, here we just
     ++	 * forcibly return to a dense checkout regardless of initial state.
     ++	 */
      +
       	argc = parse_options(argc, argv, NULL,
       			     builtin_sparse_checkout_disable_options,
  4:  82a13cc0197 =  4:  5882332b97f sparse-checkout: disallow --no-stdin as an argument to set
  5:  7a812e0222c =  5:  3e9e28c8dd2 sparse-checkout: split out code for tweaking settings config
  6:  7167a4b3118 =  6:  595ba138603 sparse-checkout: enable `set` to initialize sparse-checkout mode
  7:  3687637915f =  7:  09b13280c26 sparse-checkout: enable reapply to take --[no-]{cone,sparse-index}
  8:  7483d1363e5 =  8:  9d96da855ea git-sparse-checkout.txt: update to document init/set/reapply changes
  9:  11a45920602 =  9:  f669829a98b Documentation: clarify/correct a few sparsity related statements
 10:  395d9b194d3 = 10:  ae671aa615a clone: avoid using deprecated `sparse-checkout init`