Re: [PATCH v2 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 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             | 196 ++++++++++++++++++++------
>  t/t1091-sparse-checkout-builtin.sh    |  10 +-
>  5 files changed, 219 insertions(+), 97 deletions(-)
> 
> 
> base-commit: abe6bb3905392d5eb6b01fa6e54d7e784e0522aa
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1151%2Fnewren%2Fsparse-checkout-no-init-v2
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1151/newren/sparse-checkout-no-init-v2
> Pull-Request: https://github.com/git/git/pull/1151
> 
> Range-diff vs v1:
> 
>   1:  e41cfe3c1bb =  1:  e41cfe3c1bb sparse-checkout: pass use_stdin as a parameter instead of as a global
>   2:  6f7de8f5412 =  2:  6f7de8f5412 sparse-checkout: break apart functions for sparse_checkout_(set|add)
>   -:  ----------- >  3:  bade5e52390 sparse-checkout: add sanity-checks on initial sparsity state
>   -:  ----------- >  4:  0180bfc4a93 sparse-checkout: disallow --no-stdin as an argument to set
>   -:  ----------- >  5:  3f5255eeef9 sparse-checkout: split out code for tweaking settings config
>   3:  a90687eb4c1 !  6:  3c640f5bcef sparse-checkout: enable `set` to initialize sparse-checkout mode
>      @@ builtin/sparse-checkout.c: static int sparse_checkout_add(int argc, const char *
>        
>        static char const * const builtin_sparse_checkout_set_usage[] = {
>       -	N_("git sparse-checkout set (--stdin | <patterns>)"),
>      -+	N_("git sparse-checkout set [--cone] [--[no-]sparse-index] (--stdin | <patterns>)"),
>      ++	N_("git sparse-checkout set [--[no-]cone] [--[no-]sparse-index] (--stdin | <patterns>)"),
>        	NULL
>        };
>        
>      @@ builtin/sparse-checkout.c: static int sparse_checkout_add(int argc, const char *
>        
>        static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
>        {
>      -+	int mode, record_mode;
>      -+	const char *default_patterns[] = {"/*", "!/*/"};
>      ++	int default_patterns_nr = 2;
>      ++	const char *default_patterns[] = {"/*", "!/*/", NULL};
>       +
>        	static struct option builtin_sparse_checkout_set_options[] = {
>       +		OPT_BOOL(0, "cone", &set_opts.cone_mode,
>       +			 N_("initialize the sparse-checkout in cone mode")),
>       +		OPT_BOOL(0, "sparse-index", &set_opts.sparse_index,
>       +			 N_("toggle the use of a sparse index")),
>      - 		OPT_BOOL(0, "stdin", &set_opts.use_stdin,
>      - 			 N_("read patterns from standard in")),
>      - 		OPT_END(),
>      + 		OPT_BOOL_F(0, "stdin", &set_opts.use_stdin,
>      + 			   N_("read patterns from standard in"),
>      + 			   PARSE_OPT_NONEG),
>       @@ builtin/sparse-checkout.c: static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
>        
>        	repo_read_index(the_repository);
>      @@ builtin/sparse-checkout.c: static int sparse_checkout_set(int argc, const char *
>        			     builtin_sparse_checkout_set_usage,
>        			     PARSE_OPT_KEEP_UNKNOWN);
>        
>      -+	/* Determine if we need to record the mode; ensure sparse checkout on */
>      -+	record_mode = (set_opts.cone_mode != -1) || !core_apply_sparse_checkout;
>      -+	core_apply_sparse_checkout = 1;
>      -+
>      -+	/* If not specified, use previous definition of cone mode */
>      -+	if (set_opts.cone_mode == -1 && core_apply_sparse_checkout)
>      -+		set_opts.cone_mode = core_sparse_checkout_cone;
>      -+
>      -+	/* Set cone/non-cone mode appropriately */
>      -+	if (set_opts.cone_mode == 1) {
>      -+		mode = MODE_CONE_PATTERNS;
>      -+		core_sparse_checkout_cone = 1;
>      -+	} else {
>      -+		mode = MODE_ALL_PATTERNS;
>      -+	}
>      -+	if (record_mode && set_config(mode))
>      ++	if (update_modes(&set_opts.cone_mode, &set_opts.sparse_index))
>       +		return 1;
>       +
>      -+	/* Set sparse-index/non-sparse-index mode if specified */
>      -+	if (set_opts.sparse_index >= 0) {
>      -+		if (set_sparse_index_config(the_repository, set_opts.sparse_index) < 0)
>      -+			die(_("failed to modify sparse-index config"));
>      -+
>      -+		/* force an index rewrite */
>      -+		repo_read_index(the_repository);
>      -+		the_repository->index->updated_workdir = 1;
>      -+	}
>      -+
>       +	/*
>       +	 * Cone mode automatically specifies the toplevel directory.  For
>       +	 * non-cone mode, if nothing is specified, manually select just the
>      @@ builtin/sparse-checkout.c: static int sparse_checkout_set(int argc, const char *
>       +	 */
>       +	if (!core_sparse_checkout_cone && argc == 0) {
>       +		argv = default_patterns;
>      -+		argc = 2;
>      ++		argc = default_patterns_nr;
>       +	}
>       +
>        	return modify_pattern_list(argc, argv, set_opts.use_stdin, REPLACE);
>   -:  ----------- >  7:  acb10889a1f sparse-checkout: enable reapply to take --[no-]{cone,sparse-index}
>   4:  95d3df78b2f !  8:  17b033caf4b git-sparse-checkout.txt: update to document that set handles init
>      @@ Metadata
>       Author: Elijah Newren <newren@gmail.com>
>       
>        ## Commit message ##
>      -    git-sparse-checkout.txt: update to document that set handles init
>      +    git-sparse-checkout.txt: update to document init/set/reapply changes
>       
>           As noted in the previous commit, using separate `init` and `set` steps
>      -    with sparse-checkout result in a number of issues.  The previous commit
>      -    made `set` able to handle the work of both commands.  Update the
>      -    documentation to reflect this, and mark `init` as deprecated.
>      +    with sparse-checkout result in a number of issues.  The previous commits
>      +    made `set` able to handle the work of both commands, and enabled reapply
>      +    to tweak the {cone,sparse-index} settings.  Update the documentation to
>      +    reflect this, and mark `init` as deprecated.
>       
>           Signed-off-by: Elijah Newren <newren@gmail.com>
>       
>      @@ Documentation/git-sparse-checkout.txt: COMMANDS
>       +files that are siblings of ancestor directories. The input format
>       +matches the output of `git ls-tree --name-only`.  This includes
>       +interpreting pathnames that begin with a double quote (") as C-style
>      -+quoted strings.
>      ++quoted strings.  This may become the default in the future; --no-cone
>      ++can be passed to request non-cone mode.
>        +
>       -Use the `--[no-]sparse-index` option to toggle the use of the sparse
>       -index format. This reduces the size of the index to be more closely
>      @@ Documentation/git-sparse-checkout.txt: to rewrite your index to not be sparse. O
>        	Update the sparse-checkout file to include additional patterns.
>        	By default, these patterns are read from the command-line arguments,
>       @@ Documentation/git-sparse-checkout.txt: C-style quoted strings.
>      + 	cases, it can make sense to run `git sparse-checkout reapply` later
>      + 	after cleaning up affected paths (e.g. resolving conflicts, undoing
>      + 	or committing changes, etc.).
>      +++
>      ++The `reapply` command can also take `--[no-]cone` and `--[no-]sparse-index`
>      ++flags, with the same meaning as the flags from the `set` command, in order
>      ++to change which sparsity mode you are using without needing to also respecify
>      ++all sparsity paths.
>        
>        'disable'::
>        	Disable the `core.sparseCheckout` config setting, and restore the
>   5:  9d455f1fb51 =  9:  922a65b4019 Documentation: clarify/correct a few sparsity related statements
>   6:  2ad404874ee = 10:  d47b2c88242 clone: avoid using deprecated `sparse-checkout init`
>