[PATCH/GSoC] parse-options: Add a new nousage opt

[Chirayu Desai <chirayudesai1@gmail.com>]

* To show only error text on an error instead of the full usage
* Currently used only by commands with options "--with" or "--contains",
  such as 'tag', 'branch', 'for-each-ref'.

It now prints only
  $ git tag --contains qq
  error: malformed object name qq
instead of the full usage text after the error text.

TODO: Add tests
---
 parse-options-cb.c | 12 ++++++++----
 parse-options.c    |  5 +++++
 parse-options.h    |  6 ++++--
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/parse-options-cb.c b/parse-options-cb.c
index 239898d946..ac2ea4d674 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -85,11 +85,15 @@ int parse_opt_commits(const struct option *opt, const char *arg, int unset)
 
 	if (!arg)
 		return -1;
-	if (get_sha1(arg, sha1))
-		return error("malformed object name %s", arg);
+	if (get_sha1(arg, sha1)) {
+		error("malformed object name %s", arg);
+		return -3;
+	}
 	commit = lookup_commit_reference(sha1);
-	if (!commit)
-		return error("no such commit %s", arg);
+	if (!commit) {
+		error("no such commit %s", arg);
+		return -3;
+	}
 	commit_list_insert(commit, opt->value);
 	return 0;
 }
diff --git a/parse-options.c b/parse-options.c
index 47a9192060..d136c1afd0 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -158,6 +158,9 @@ static int get_value(struct parse_opt_ctx_t *p,
 			return (*opt->callback)(opt, NULL, 0) ? (-1) : 0;
 		if (get_arg(p, opt, flags, &arg))
 			return -1;
+		if (opt->flags & PARSE_OPT_NOUSAGE) {
+			return (*opt->callback)(opt, arg, 0);
+		}
 		return (*opt->callback)(opt, arg, 0) ? (-1) : 0;
 
 	case OPTION_INTEGER:
@@ -504,6 +507,8 @@ int parse_options_step(struct parse_opt_ctx_t *ctx,
 			goto show_usage_error;
 		case -2:
 			goto unknown;
+		case -3:
+			return PARSE_OPT_DONE;
 		}
 		continue;
 unknown:
diff --git a/parse-options.h b/parse-options.h
index ea4af92a51..628e34c5af 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -38,7 +38,8 @@ enum parse_opt_option_flags {
 	PARSE_OPT_LASTARG_DEFAULT = 16,
 	PARSE_OPT_NODASH = 32,
 	PARSE_OPT_LITERAL_ARGHELP = 64,
-	PARSE_OPT_SHELL_EVAL = 256
+	PARSE_OPT_SHELL_EVAL = 256,
+	PARSE_OPT_NOUSAGE = 512
 };
 
 struct option;
@@ -89,6 +90,7 @@ typedef int parse_opt_ll_cb(struct parse_opt_ctx_t *ctx,
  *   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_NOUSAGE: do not print usage / help on error.
  *
  * `callback`::
  *   pointer to the callback to use for OPTION_CALLBACK or
@@ -254,7 +256,7 @@ extern int parse_opt_passthru_argv(const struct option *, const char *, int);
 	{ OPTION_CALLBACK, (s), (l), (v), (a), (h), (f), parse_opt_passthru_argv }
 #define _OPT_CONTAINS_OR_WITH(name, variable, help, flag) \
 	{ OPTION_CALLBACK, 0, name, (variable), N_("commit"), (help), \
-	  PARSE_OPT_LASTARG_DEFAULT | flag, \
+	  PARSE_OPT_LASTARG_DEFAULT | PARSE_OPT_NOUSAGE | flag, \
 	  parse_opt_commits, (intptr_t) "HEAD" \
 	}
 #define OPT_CONTAINS(v, h) _OPT_CONTAINS_OR_WITH("contains", v, h, 0)
-- 
2.7.4