scalar: implement the `version` command

The .NET version of Scalar has a `version` command. This was necessary
because it was versioned independently of Git.

Since Scalar is now tightly coupled with Git, it does not make sense for
them to show different versions. Therefore, it shows the same output as
`git version`. For backwards-compatibility with the .NET version,
`scalar version` prints to `stderr`, though (`git version` prints to
`stdout` instead).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/scalar/scalar.c

@@ -10,6 +10,7 @@
 #include "refs.h"
 #include "dir.h"
 #include "packfile.h"
+#include "help.h"
 
 /*
  * Remove the deepest subdirectory in the provided path string. Path must not
@@ -357,6 +358,15 @@ static int delete_enlistment(struct strbuf *enlistment)
 	return 0;
 }
 
+/*
+ * Dummy implementation; Using `get_version_info()` would cause a link error
+ * without this.
+ */
+void load_builtin_commands(const char *prefix, struct cmdnames *cmds)
+{
+	die("not implemented");
+}
+
 static int cmd_clone(int argc, const char **argv)
 {
 	const char *branch = NULL;
@@ -750,6 +760,34 @@ static int cmd_delete(int argc, const char **argv)
 	return res;
 }
 
+static int cmd_version(int argc, const char **argv)
+{
+	int verbose = 0, build_options = 0;
+	struct option options[] = {
+		OPT__VERBOSE(&verbose, N_("include Git version")),
+		OPT_BOOL(0, "build-options", &build_options,
+			 N_("include Git's build options")),
+		OPT_END(),
+	};
+	const char * const usage[] = {
+		N_("scalar verbose [-v | --verbose] [--build-options]"),
+		NULL
+	};
+	struct strbuf buf = STRBUF_INIT;
+
+	argc = parse_options(argc, argv, NULL, options,
+			     usage, 0);
+
+	if (argc != 0)
+		usage_with_options(usage, options);
+
+	get_version_info(&buf, build_options);
+	fprintf(stderr, "%s\n", buf.buf);
+	strbuf_release(&buf);
+
+	return 0;
+}
+
 static struct {
 	const char *name;
 	int (*fn)(int, const char **);
@@ -761,6 +799,7 @@ static struct {
 	{ "run", cmd_run },
 	{ "reconfigure", cmd_reconfigure },
 	{ "delete", cmd_delete },
+	{ "version", cmd_version },
 	{ NULL, NULL},
 };