[PATCH v2 01/19] parse-options-cb: implement parse_opt_pass_strbuf()

[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_pass_strbuf() parse-options callback, which will
reconstruct the command-line option into an strbuf, such that it can be
passed to another git command.

Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Paul Tan <pyokagan@gmail.com>
---

Notes:
    v2
    
    * Previously implemented as a static function in builtin/pull.c. It now
      uses an strbuf instead of returning newly-allocated strings, to make
      memory management easier.
    
    * We don't use defval anymore. Instead, we use long_name and short_name.

 parse-options-cb.c | 29 +++++++++++++++++++++++++++++
 parse-options.h    |  1 +
 2 files changed, 30 insertions(+)

diff --git a/parse-options-cb.c b/parse-options-cb.c
index be8c413..5b1dbcf 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -134,3 +134,32 @@ int parse_opt_noop_cb(const struct option *opt, const char *arg, int unset)
 {
 	return 0;
 }
+
+/**
+ * For an option opt, recreates the command-line option in opt->value which
+ * must be an strbuf. This is useful when we need to pass the command-line
+ * option to another command.
+ */
+int parse_opt_pass_strbuf(const struct option *opt, const char *arg, int unset)
+{
+	struct strbuf *sb = opt->value;
+
+	strbuf_reset(sb);
+
+	if (opt->long_name) {
+		strbuf_addstr(sb, unset ? "--no-" : "--");
+		strbuf_addstr(sb, opt->long_name);
+		if (arg) {
+			strbuf_addch(sb, '=');
+			strbuf_addstr(sb, arg);
+		}
+	} else if (opt->short_name && !unset) {
+		strbuf_addch(sb, '-');
+		strbuf_addch(sb, opt->short_name);
+		if (arg)
+			strbuf_addstr(sb, arg);
+	} else
+		return -1;
+
+	return 0;
+}
diff --git a/parse-options.h b/parse-options.h
index c71e9da..1d21398 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -224,6 +224,7 @@ extern int parse_opt_with_commit(const struct option *, const char *, int);
 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_pass_strbuf(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))
-- 
2.1.4