[PATCH v3 02/19] parse-options-cb: implement parse_opt_passthru_argv()

[Paul Tan <pyokagan@gmail.com>]

Certain git commands, such as git-pull, are simply wrappers around other
git commands like git-fetch, git-merge and git-rebase. As such, these
wrapper commands will typically need to "pass through" command-line
options of the commands they wrap.

Implement the parse_opt_passthru_argv() parse-options callback, which
will reconstruct all the provided command-line options into an
argv_array, such that it can be passed to another git command. This is
useful for passing command-line options that can be specified multiple
times.

Helped-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Paul Tan <pyokagan@gmail.com>
---

Notes:
    v3
    
    * Renamed function to the more descriptive parse_opt_passthru_argv().
    
    * Introduced and documented OPT_PASSTHRU_ARGV() macro, which saves the
      user from having to specify OPTION_CALLBACK and
      parse_opt_passthru_argv() for each option.

 Documentation/technical/api-parse-options.txt |  6 ++++++
 parse-options-cb.c                            | 20 ++++++++++++++++++++
 parse-options.h                               |  3 +++
 3 files changed, 29 insertions(+)

diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt
index 85d10ab..0b0ab01 100644
--- a/Documentation/technical/api-parse-options.txt
+++ b/Documentation/technical/api-parse-options.txt
@@ -219,6 +219,12 @@ There are some macros to easily define options:
 	will be overwritten, so this should only be used for options where
 	the last one specified on the command line wins.
 
+`OPT_PASSTHRU_ARGV(short, long, &argv_array_var, arg_str, description, flags)`::
+	Introduce an option where all instances of it on the command-line will
+	be reconstructed into an argv_array. This is useful when you need to
+	pass the command-line option, which can be specified multiple times,
+	to another command.
+
 
 The last element of the array must be `OPT_END()`.
 
diff --git a/parse-options-cb.c b/parse-options-cb.c
index 68bc593..5ab6ed6 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -4,6 +4,7 @@
 #include "commit.h"
 #include "color.h"
 #include "string-list.h"
+#include "argv-array.h"
 
 /*----- some often used options -----*/
 
@@ -183,3 +184,22 @@ int parse_opt_passthru(const struct option *opt, const char *arg, int unset)
 
 	return 0;
 }
+
+/**
+ * For an option opt, recreate the command-line option, appending it to
+ * opt->value which must be a argv_array. This is useful when we need to pass
+ * the command-line option, which can be specified multiple times, to another
+ * command.
+ */
+int parse_opt_passthru_argv(const struct option *opt, const char *arg, int unset)
+{
+	static struct strbuf sb = STRBUF_INIT;
+	struct argv_array *opt_value = opt->value;
+
+	if (recreate_opt(&sb, opt, arg, unset) < 0)
+		return -1;
+
+	argv_array_push(opt_value, sb.buf);
+
+	return 0;
+}
diff --git a/parse-options.h b/parse-options.h
index 5b0f886..aba06688 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -225,6 +225,7 @@ extern int parse_opt_tertiary(const struct option *, const char *, int);
 extern int parse_opt_string_list(const struct option *, const char *, int);
 extern int parse_opt_noop_cb(const struct option *, const char *, int);
 extern int parse_opt_passthru(const struct option *, const char *, int);
+extern int parse_opt_passthru_argv(const struct option *, const char *, int);
 
 #define OPT__VERBOSE(var, h)  OPT_COUNTUP('v', "verbose", (var), (h))
 #define OPT__QUIET(var, h)    OPT_COUNTUP('q', "quiet",   (var), (h))
@@ -245,5 +246,7 @@ extern int parse_opt_passthru(const struct option *, const char *, int);
 	{ OPTION_CALLBACK, (s), (l), (v), N_("style"), (h), PARSE_OPT_OPTARG, parseopt_column_callback }
 #define OPT_PASSTHRU(s, l, v, a, h, f) \
 	{ OPTION_CALLBACK, (s), (l), (v), (a), (h), (f), parse_opt_passthru }
+#define OPT_PASSTHRU_ARGV(s, l, v, a, h, f) \
+	{ OPTION_CALLBACK, (s), (l), (v), (a), (h), (f), parse_opt_passthru_argv }
 
 #endif
-- 
2.1.4