merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/builtin/var.c

@@ -0,0 +1,94 @@
+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) Eric Biederman, 2005
+ */
+#include "builtin.h"
+#include "config.h"
+
+static const char var_usage[] = "git var (-l | <variable>)";
+
+static const char *editor(int flag)
+{
+	const char *pgm = git_editor();
+
+	if (!pgm && flag & IDENT_STRICT)
+		die("Terminal is dumb, but EDITOR unset");
+
+	return pgm;
+}
+
+static const char *pager(int flag)
+{
+	const char *pgm = git_pager(1);
+
+	if (!pgm)
+		pgm = "cat";
+	return pgm;
+}
+
+struct git_var {
+	const char *name;
+	const char *(*read)(int);
+};
+static struct git_var git_vars[] = {
+	{ "GIT_COMMITTER_IDENT", git_committer_info },
+	{ "GIT_AUTHOR_IDENT",   git_author_info },
+	{ "GIT_EDITOR", editor },
+	{ "GIT_PAGER", pager },
+	{ "", NULL },
+};
+
+static void list_vars(void)
+{
+	struct git_var *ptr;
+	const char *val;
+
+	for (ptr = git_vars; ptr->read; ptr++)
+		if ((val = ptr->read(0)))
+			printf("%s=%s\n", ptr->name, val);
+}
+
+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(IDENT_STRICT);
+			break;
+		}
+	}
+	return val;
+}
+
+static int show_config(const char *var, const char *value, void *cb)
+{
+	if (value)
+		printf("%s=%s\n", var, value);
+	else
+		printf("%s\n", var);
+	return git_default_config(var, value, cb);
+}
+
+int cmd_var(int argc, const char **argv, const char *prefix)
+{
+	const char *val = NULL;
+	if (argc != 2)
+		usage(var_usage);
+
+	if (strcmp(argv[1], "-l") == 0) {
+		git_config(show_config, NULL);
+		list_vars();
+		return 0;
+	}
+	git_config(git_default_config, NULL);
+	val = read_var(argv[1]);
+	if (!val)
+		usage(var_usage);
+
+	printf("%s\n", val);
+
+	return 0;
+}