[PATCH] Add git-var a tool for reading interesting git variables.

Sharing code between shell scripts and C is a challenge.  The program
git-var allows us to have a set of named values that a shell script can
interrogate and a normal C program can simply call the functions that
compute them.  Allowing sharing when computing plain test values.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

var.c

@@ -0,0 +1,65 @@
+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) Eric Biederman, 2005
+ */
+#include "cache.h"
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+
+static char *var_usage = "git-var [-l | <variable>]";
+
+struct git_var {
+	const char *name;
+	char *(*read)(void);
+};
+static struct git_var git_vars[] = {
+	{ "GIT_COMMITTER_IDENT", git_committer_info },
+	{ "GIT_AUTHOR_IDENT",   git_author_info },
+	{ "", NULL },
+};
+
+static void list_vars(void)
+{
+	struct git_var *ptr;
+	for(ptr = git_vars; ptr->read; ptr++) {
+		printf("%s=%s\n", ptr->name, ptr->read());
+	}
+}
+
+static const char *read_var(const char *var)
+{
+	struct git_var *ptr;
+	const char *val;
+	val = NULL;
+	for(ptr = git_vars; ptr->read; ptr++) {
+		if (strcmp(var, ptr->name) == 0) {
+			val = ptr->read();
+			break;
+		}
+	}
+	return val;
+}
+
+int main(int argc, char **argv)
+{
+	const char *val;
+	if (argc != 2) {
+		usage(var_usage);
+	}
+	setup_ident();
+	val = NULL;
+
+	if (strcmp(argv[1], "-l") == 0) {
+		list_vars();
+		return 0;
+	}
+	val = read_var(argv[1]);
+	if (!val)
+		usage(var_usage);
+	
+	printf("%s\n", val);
+	
+	return 0;
+}