[PATCH 1/4] parse-options: allow git commands to invent new option types

[Jonathan Nieder <jrnieder@gmail.com>]

parse-options provides a variety of option behaviors, including
OPTION_CALLBACK, which should take care of just about any sane
behavior.  All supported behaviors obey the following constraint:

 A --foo option can only accept (and base its behavior on)
 one argument, which would be the following command-line
 argument in the "unsticked" form.

Alas, some existing git commands have options that do not obey that
constraint.  For example, update-index --cacheinfo takes three
arguments, and update-index --resolve takes all later parameters as
arguments.

Introduce a new option type (OPTION_LOWLEVEL_CALLBACK) to support
such unusual options.  parse_options() callers can implement an
arbitrary custom get_value() function to override the usual one and
pass it through the callback field for options of interest.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
 parse-options.c |    6 +++---
 parse-options.h |    9 +++++++++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/parse-options.c b/parse-options.c
index 0fa79bc..7907306 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -8,9 +8,6 @@ static int parse_options_usage(struct parse_opt_ctx_t *ctx,
 			       const char * const *usagestr,
 			       const struct option *opts, int err);
 
-#define OPT_SHORT 1
-#define OPT_UNSET 2
-
 static int opterror(const struct option *opt, const char *reason, int flags)
 {
 	if (flags & OPT_SHORT)
@@ -51,6 +48,9 @@ static int get_value(struct parse_opt_ctx_t *p,
 	const int unset = flags & OPT_UNSET;
 	int err;
 
+	if (opt->type == OPTION_LOWLEVEL_CALLBACK)
+		return (*(parse_opt_ll_cb *)opt->callback)(p, opt, flags);
+
 	if (unset && p->opt)
 		return opterror(opt, "takes no value", flags);
 	if (unset && (opt->flags & PARSE_OPT_NONEG))
diff --git a/parse-options.h b/parse-options.h
index d982f0f..fa400da 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -17,6 +17,7 @@ enum parse_opt_type {
 	OPTION_STRING,
 	OPTION_INTEGER,
 	OPTION_CALLBACK,
+	OPTION_LOWLEVEL_CALLBACK,
 	OPTION_FILENAME
 };
 
@@ -40,8 +41,16 @@ enum parse_opt_option_flags {
 	PARSE_OPT_SHELL_EVAL = 256
 };
 
+enum parse_opt_ll_flags {
+	OPT_SHORT = 1,
+	OPT_UNSET = 2
+};
+
 struct option;
+struct parse_opt_ctx_t;
 typedef int parse_opt_cb(const struct option *, const char *arg, int unset);
+typedef int parse_opt_ll_cb(struct parse_opt_ctx_t *ctx,
+			    const struct option *opt, int flags);
 
 /*
  * `type`::
-- 
1.7.2.3