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df217ed643
Commit dbd0f5c
(Files given on the command line are relative to $cwd,
2008-08-06) introduced parse_options_fix_filename() as a minimal fix.
OPT_FILENAME is intended to be a more robust fix for the same issue.
OPT_FILENAME and its associated enum OPTION_FILENAME are used to
represent filename options within the parse options API.
This option is similar to OPTION_STRING. If --no is prefixed to the
option the filename is unset. If no argument is given and the default
value is set, the filename is set to the default value. The difference
is that the filename is prefixed with the prefix passed to
parse_options() (or parse_options_start()).
Update git-apply, git-commit, git-fmt-merge-msg, and git-tag to use
OPT_FILENAME with their filename options. Also, rename
parse_options_fix_filename() to fix_filename() as it is no longer
extern.
Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
251 lines
8.2 KiB
Text
251 lines
8.2 KiB
Text
parse-options API
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=================
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The parse-options API is used to parse and massage options in git
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and to provide a usage help with consistent look.
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Basics
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------
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The argument vector `argv[]` may usually contain mandatory or optional
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'non-option arguments', e.g. a filename or a branch, and 'options'.
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Options are optional arguments that start with a dash and
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that allow to change the behavior of a command.
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* There are basically three types of options:
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'boolean' options,
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options with (mandatory) 'arguments' and
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options with 'optional arguments'
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(i.e. a boolean option that can be adjusted).
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* There are basically two forms of options:
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'Short options' consist of one dash (`-`) and one alphanumeric
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character.
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'Long options' begin with two dashes (`\--`) and some
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alphanumeric characters.
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* Options are case-sensitive.
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Please define 'lower-case long options' only.
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The parse-options API allows:
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* 'sticked' and 'separate form' of options with arguments.
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`-oArg` is sticked, `-o Arg` is separate form.
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`\--option=Arg` is sticked, `\--option Arg` is separate form.
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* Long options may be 'abbreviated', as long as the abbreviation
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is unambiguous.
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* Short options may be bundled, e.g. `-a -b` can be specified as `-ab`.
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* Boolean long options can be 'negated' (or 'unset') by prepending
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`no-`, e.g. `\--no-abbrev` instead of `\--abbrev`.
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* Options and non-option arguments can clearly be separated using the `\--`
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option, e.g. `-a -b \--option \-- \--this-is-a-file` indicates that
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`\--this-is-a-file` must not be processed as an option.
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Steps to parse options
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----------------------
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. `#include "parse-options.h"`
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. define a NULL-terminated
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`static const char * const builtin_foo_usage[]` array
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containing alternative usage strings
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. define `builtin_foo_options` array as described below
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in section 'Data Structure'.
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. in `cmd_foo(int argc, const char **argv, const char *prefix)`
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call
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argc = parse_options(argc, argv, prefix, builtin_foo_options, builtin_foo_usage, flags);
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+
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`parse_options()` will filter out the processed options of `argv[]` and leave the
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non-option arguments in `argv[]`.
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`argc` is updated appropriately because of the assignment.
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+
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You can also pass NULL instead of a usage array as the fifth parameter of
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parse_options(), to avoid displaying a help screen with usage info and
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option list. This should only be done if necessary, e.g. to implement
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a limited parser for only a subset of the options that needs to be run
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before the full parser, which in turn shows the full help message.
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+
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Flags are the bitwise-or of:
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`PARSE_OPT_KEEP_DASHDASH`::
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Keep the `\--` that usually separates options from
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non-option arguments.
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`PARSE_OPT_STOP_AT_NON_OPTION`::
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Usually the whole argument vector is massaged and reordered.
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Using this flag, processing is stopped at the first non-option
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argument.
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`PARSE_OPT_KEEP_ARGV0`::
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Keep the first argument, which contains the program name. It's
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removed from argv[] by default.
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`PARSE_OPT_KEEP_UNKNOWN`::
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Keep unknown arguments instead of erroring out. This doesn't
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work for all combinations of arguments as users might expect
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it to do. E.g. if the first argument in `--unknown --known`
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takes a value (which we can't know), the second one is
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mistakenly interpreted as a known option. Similarly, if
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`PARSE_OPT_STOP_AT_NON_OPTION` is set, the second argument in
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`--unknown value` will be mistakenly interpreted as a
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non-option, not as a value belonging to the unknown option,
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the parser early. That's why parse_options() errors out if
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both options are set.
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`PARSE_OPT_NO_INTERNAL_HELP`::
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By default, parse_options() handles `-h`, `--help` and
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`--help-all` internally, by showing a help screen. This option
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turns it off and allows one to add custom handlers for these
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options, or to just leave them unknown.
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Data Structure
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--------------
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The main data structure is an array of the `option` struct,
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say `static struct option builtin_add_options[]`.
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There are some macros to easily define options:
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`OPT__ABBREV(&int_var)`::
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Add `\--abbrev[=<n>]`.
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`OPT__DRY_RUN(&int_var)`::
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Add `-n, \--dry-run`.
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`OPT__QUIET(&int_var)`::
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Add `-q, \--quiet`.
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`OPT__VERBOSE(&int_var)`::
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Add `-v, \--verbose`.
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`OPT_GROUP(description)`::
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Start an option group. `description` is a short string that
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describes the group or an empty string.
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Start the description with an upper-case letter.
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`OPT_BOOLEAN(short, long, &int_var, description)`::
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Introduce a boolean option.
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`int_var` is incremented on each use.
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`OPT_BIT(short, long, &int_var, description, mask)`::
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Introduce a boolean option.
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If used, `int_var` is bitwise-ored with `mask`.
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`OPT_NEGBIT(short, long, &int_var, description, mask)`::
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Introduce a boolean option.
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If used, `int_var` is bitwise-anded with the inverted `mask`.
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`OPT_SET_INT(short, long, &int_var, description, integer)`::
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Introduce a boolean option.
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If used, set `int_var` to `integer`.
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`OPT_SET_PTR(short, long, &ptr_var, description, ptr)`::
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Introduce a boolean option.
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If used, set `ptr_var` to `ptr`.
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`OPT_STRING(short, long, &str_var, arg_str, description)`::
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Introduce an option with string argument.
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The string argument is put into `str_var`.
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`OPT_INTEGER(short, long, &int_var, description)`::
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Introduce an option with integer argument.
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The integer is put into `int_var`.
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`OPT_DATE(short, long, &int_var, description)`::
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Introduce an option with date argument, see `approxidate()`.
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The timestamp is put into `int_var`.
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`OPT_CALLBACK(short, long, &var, arg_str, description, func_ptr)`::
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Introduce an option with argument.
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The argument will be fed into the function given by `func_ptr`
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and the result will be put into `var`.
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See 'Option Callbacks' below for a more elaborate description.
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`OPT_FILENAME(short, long, &var, description)`::
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Introduce an option with a filename argument.
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The filename will be prefixed by passing the filename along with
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the prefix argument of `parse_options()` to `prefix_filename()`.
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`OPT_ARGUMENT(long, description)`::
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Introduce a long-option argument that will be kept in `argv[]`.
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`OPT_NUMBER_CALLBACK(&var, description, func_ptr)`::
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Recognize numerical options like -123 and feed the integer as
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if it was an argument to the function given by `func_ptr`.
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The result will be put into `var`. There can be only one such
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option definition. It cannot be negated and it takes no
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arguments. Short options that happen to be digits take
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precedence over it.
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The last element of the array must be `OPT_END()`.
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If not stated otherwise, interpret the arguments as follows:
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* `short` is a character for the short option
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(e.g. `\'e\'` for `-e`, use `0` to omit),
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* `long` is a string for the long option
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(e.g. `"example"` for `\--example`, use `NULL` to omit),
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* `int_var` is an integer variable,
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* `str_var` is a string variable (`char *`),
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* `arg_str` is the string that is shown as argument
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(e.g. `"branch"` will result in `<branch>`).
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If set to `NULL`, three dots (`...`) will be displayed.
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* `description` is a short string to describe the effect of the option.
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It shall begin with a lower-case letter and a full stop (`.`) shall be
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omitted at the end.
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Option Callbacks
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----------------
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The function must be defined in this form:
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int func(const struct option *opt, const char *arg, int unset)
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The callback mechanism is as follows:
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* Inside `func`, the only interesting member of the structure
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given by `opt` is the void pointer `opt->value`.
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`\*opt->value` will be the value that is saved into `var`, if you
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use `OPT_CALLBACK()`.
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For example, do `*(unsigned long *)opt->value = 42;` to get 42
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into an `unsigned long` variable.
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* Return value `0` indicates success and non-zero return
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value will invoke `usage_with_options()` and, thus, die.
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* If the user negates the option, `arg` is `NULL` and `unset` is 1.
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Sophisticated option parsing
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----------------------------
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If you need, for example, option callbacks with optional arguments
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or without arguments at all, or if you need other special cases,
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that are not handled by the macros above, you need to specify the
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members of the `option` structure manually.
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This is not covered in this document, but well documented
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in `parse-options.h` itself.
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Examples
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--------
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See `test-parse-options.c` and
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`builtin-add.c`,
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`builtin-clone.c`,
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`builtin-commit.c`,
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`builtin-fetch.c`,
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`builtin-fsck.c`,
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`builtin-rm.c`
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for real-world examples.
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