text: #ifndef PARSE_OPTIONS_H
  #define PARSE_OPTIONS_H
  
  enum parse_opt_type {
  	/* special types */
  	OPTION_END,
  	OPTION_ARGUMENT,
  	OPTION_GROUP,
  	OPTION_NUMBER,
  	/* options with no arguments */
  	OPTION_BIT,
  	OPTION_NEGBIT,
  	OPTION_BOOLEAN, /* _INCR would have been a better name */
  	OPTION_SET_INT,
  	OPTION_SET_PTR,
  	/* options with arguments (usually) */
  	OPTION_STRING,
  	OPTION_INTEGER,
  	OPTION_CALLBACK,
  	OPTION_LOWLEVEL_CALLBACK,
  	OPTION_FILENAME
  };
  
  enum parse_opt_flags {
  	PARSE_OPT_KEEP_DASHDASH = 1,
  	PARSE_OPT_STOP_AT_NON_OPTION = 2,
  	PARSE_OPT_KEEP_ARGV0 = 4,
  	PARSE_OPT_KEEP_UNKNOWN = 8,
  	PARSE_OPT_NO_INTERNAL_HELP = 16
  };
  
  enum parse_opt_option_flags {
  	PARSE_OPT_OPTARG  = 1,
  	PARSE_OPT_NOARG   = 2,
  	PARSE_OPT_NONEG   = 4,
  	PARSE_OPT_HIDDEN  = 8,
  	PARSE_OPT_LASTARG_DEFAULT = 16,
  	PARSE_OPT_NODASH = 32,
  	PARSE_OPT_LITERAL_ARGHELP = 64,
  	PARSE_OPT_NEGHELP = 128,
  	PARSE_OPT_SHELL_EVAL = 256
  };
  
  struct option;
  typedef int parse_opt_cb(const struct option *, const char *arg, int unset);
  
  struct parse_opt_ctx_t;
  typedef int parse_opt_ll_cb(struct parse_opt_ctx_t *ctx,
  				const struct option *opt, int unset);
  
  /*
   * `type`::
   *   holds the type of the option, you must have an OPTION_END last in your
   *   array.
   *
   * `short_name`::
   *   the character to use as a short option name, '\0' if none.
   *
   * `long_name`::
   *   the long option name, without the leading dashes, NULL if none.
   *
   * `value`::
   *   stores pointers to the values to be filled.
   *
   * `argh`::
   *   token to explain the kind of argument this option wants. Keep it
   *   homogeneous across the repository.
   *
   * `help`::
   *   the short help associated to what the option does.
   *   Must never be NULL (except for OPTION_END).
   *   OPTION_GROUP uses this pointer to store the group header.
   *
   * `flags`::
   *   mask of parse_opt_option_flags.
   *   PARSE_OPT_OPTARG: says that the argument is optional (not for BOOLEANs)
   *   PARSE_OPT_NOARG: says that this option does not take an argument
   *   PARSE_OPT_NONEG: says that this option cannot be negated
   *   PARSE_OPT_HIDDEN: this option is skipped in the default usage, and
   *                     shown only in the full usage.
   *   PARSE_OPT_LASTARG_DEFAULT: says that this option will take the default
   *				value if no argument is given when the option
   *				is last on the command line. If the option is
   *				not last it will require an argument.
   *				Should not be used with PARSE_OPT_OPTARG.
   *   PARSE_OPT_NODASH: this option doesn't start with a dash.
   *   PARSE_OPT_LITERAL_ARGHELP: says that argh shouldn't be enclosed in brackets
   *				(i.e. '<argh>') in the help message.
   *				Useful for options with multiple parameters.
   *   PARSE_OPT_NEGHELP: says that the long option should always be shown with
   *				the --no prefix in the usage message. Sometimes
   *				useful for users of OPTION_NEGBIT.
   *
   * `callback`::
   *   pointer to the callback to use for OPTION_CALLBACK or
   *   OPTION_LOWLEVEL_CALLBACK.
   *
   * `defval`::
   *   default value to fill (*->value) with for PARSE_OPT_OPTARG.
   *   OPTION_{BIT,SET_INT,SET_PTR} store the {mask,integer,pointer} to put in
   *   the value when met.
   *   CALLBACKS can use it like they want.
   */
  struct option {
  	enum parse_opt_type type;
  	int short_name;
  	const char *long_name;
  	void *value;
  	const char *argh;
  	const char *help;
  
  	int flags;
  	parse_opt_cb *callback;
  	intptr_t defval;
  };
  
  #define OPT_END()                   { OPTION_END }
  #define OPT_ARGUMENT(l, h)          { OPTION_ARGUMENT, 0, (l), NULL, NULL, \
  				      (h), PARSE_OPT_NOARG}
  #define OPT_GROUP(h)                { OPTION_GROUP, 0, NULL, NULL, NULL, (h) }
  #define OPT_BIT(s, l, v, h, b)      { OPTION_BIT, (s), (l), (v), NULL, (h), \
  				      PARSE_OPT_NOARG, NULL, (b) }
  #define OPT_NEGBIT(s, l, v, h, b)   { OPTION_NEGBIT, (s), (l), (v), NULL, \
  				      (h), PARSE_OPT_NOARG, NULL, (b) }
  #define OPT_BOOLEAN(s, l, v, h)     { OPTION_BOOLEAN, (s), (l), (v), NULL, \
  				      (h), PARSE_OPT_NOARG }
  #define OPT_SET_INT(s, l, v, h, i)  { OPTION_SET_INT, (s), (l), (v), NULL, \
  				      (h), PARSE_OPT_NOARG, NULL, (i) }
  #define OPT_SET_PTR(s, l, v, h, p)  { OPTION_SET_PTR, (s), (l), (v), NULL, \
  				      (h), PARSE_OPT_NOARG, NULL, (p) }
  #define OPT_INTEGER(s, l, v, h)     { OPTION_INTEGER, (s), (l), (v), "n", (h) }
  #define OPT_STRING(s, l, v, a, h)   { OPTION_STRING,  (s), (l), (v), (a), (h) }
  #define OPT_UYN(s, l, v, h)         { OPTION_CALLBACK, (s), (l), (v), NULL, \
  				      (h), PARSE_OPT_NOARG, &parse_opt_tertiary }
  #define OPT_DATE(s, l, v, h) \
  	{ OPTION_CALLBACK, (s), (l), (v), "time",(h), 0, \
  	  parse_opt_approxidate_cb }
  #define OPT_CALLBACK(s, l, v, a, h, f) \
  	{ OPTION_CALLBACK, (s), (l), (v), (a), (h), 0, (f) }
  #define OPT_NUMBER_CALLBACK(v, h, f) \
  	{ OPTION_NUMBER, 0, NULL, (v), NULL, (h), \
  	  PARSE_OPT_NOARG | PARSE_OPT_NONEG, (f) }
  #define OPT_FILENAME(s, l, v, h)    { OPTION_FILENAME, (s), (l), (v), \
  				       "file", (h) }
  #define OPT_COLOR_FLAG(s, l, v, h) \
  	{ OPTION_CALLBACK, (s), (l), (v), "when", (h), PARSE_OPT_OPTARG, \
  		parse_opt_color_flag_cb, (intptr_t)"always" }
  
  
  /* parse_options() will filter out the processed options and leave the
   * non-option arguments in argv[].
   * Returns the number of arguments left in argv[].
   */
  extern int parse_options(int argc, const char **argv, const char *prefix,
                           const struct option *options,
                           const char * const usagestr[], int flags);
  
  extern NORETURN void usage_with_options(const char * const *usagestr,
                                          const struct option *options);
  
  extern NORETURN void usage_msg_opt(const char *msg,
  				   const char * const *usagestr,
  				   const struct option *options);
  
  /*----- incremental advanced APIs -----*/
  
  enum {
  	PARSE_OPT_HELP = -1,
  	PARSE_OPT_DONE,
  	PARSE_OPT_NON_OPTION,
  	PARSE_OPT_UNKNOWN
  };
  
  /*
   * It's okay for the caller to consume argv/argc in the usual way.
   * Other fields of that structure are private to parse-options and should not
   * be modified in any way.
   */
  struct parse_opt_ctx_t {
  	const char **argv;
  	const char **out;
  	int argc, cpidx;
  	const char *opt;
  	int flags;
  	const char *prefix;
  };
  
  extern void parse_options_start(struct parse_opt_ctx_t *ctx,
  				int argc, const char **argv, const char *prefix,
  				const struct option *options, int flags);
  
  extern int parse_options_step(struct parse_opt_ctx_t *ctx,
  			      const struct option *options,
  			      const char * const usagestr[]);
  
  extern int parse_options_end(struct parse_opt_ctx_t *ctx);
  
  extern int parse_options_concat(struct option *dst, size_t, struct option *src);
  
  /*----- some often used options -----*/
  extern int parse_opt_abbrev_cb(const struct option *, const char *, int);
  extern int parse_opt_approxidate_cb(const struct option *, const char *, int);
  extern int parse_opt_color_flag_cb(const struct option *, const char *, int);
  extern int parse_opt_verbosity_cb(const struct option *, const char *, int);
  extern int parse_opt_with_commit(const struct option *, const char *, int);
  extern int parse_opt_tertiary(const struct option *, const char *, int);
  
  #define OPT__VERBOSE(var, h)  OPT_BOOLEAN('v', "verbose", (var), (h))
  #define OPT__QUIET(var, h)    OPT_BOOLEAN('q', "quiet",   (var), (h))
  #define OPT__VERBOSITY(var) \
  	{ OPTION_CALLBACK, 'v', "verbose", (var), NULL, "be more verbose", \
  	  PARSE_OPT_NOARG, &parse_opt_verbosity_cb, 0 }, \
  	{ OPTION_CALLBACK, 'q', "quiet", (var), NULL, "be more quiet", \
  	  PARSE_OPT_NOARG, &parse_opt_verbosity_cb, 0 }
  #define OPT__DRY_RUN(var, h)  OPT_BOOLEAN('n', "dry-run", (var), (h))
  #define OPT__FORCE(var, h)    OPT_BOOLEAN('f', "force",   (var), (h))
  #define OPT__ABBREV(var)  \
  	{ OPTION_CALLBACK, 0, "abbrev", (var), "n", \
  	  "use <n> digits to display SHA-1s", \
  	  PARSE_OPT_OPTARG, &parse_opt_abbrev_cb, 0 }
  #define OPT__COLOR(var, h) \
  	OPT_COLOR_FLAG(0, "color", (var), (h))
  
  #endif
  