update-index: teach --cacheinfo a new syntax "mode,sha1,path"

The "--cacheinfo" option is unusual in that it takes three option
parameters.  An option with an optional parameter is bad enough.  An
option with multiple parameters is simply insane.

Introduce a new syntax that takes these three things concatenated
together with a comma, which makes the command line syntax more
uniform across subcommands, while retaining the traditional syntax
for backward compatiblity.

If we were designing the "update-index" subcommand from scratch
today, it may probably have made sense to make this option (and
possibly others) a command mode option that does not take any option
parameter (hence no need for arg-help).  But we do not live in such
an ideal world, and as far as I can tell, the command still supports
(and must support) mixed command modes in a single invocation, e.g.

    $ git update-index path1 --add path2 \
        --cacheinfo 100644 $(git hash-object --stdin -w <path3) path3 \
	path4

must make sure path1 is already in the index and update all of these
four paths.  So this is probably as far as we can go to fix this issue
without risking to break people's existing scripts.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-update-index.txt

@@ -12,7 +12,7 @@ SYNOPSIS
 'git update-index'
 	     [--add] [--remove | --force-remove] [--replace]
 	     [--refresh] [-q] [--unmerged] [--ignore-missing]
-	     [(--cacheinfo <mode> <object> <file>)...]
+	     [(--cacheinfo <mode>,<object>,<file>)...]
 	     [--chmod=(+|-)x]
 	     [--[no-]assume-unchanged]
 	     [--[no-]skip-worktree]
@@ -68,8 +68,12 @@ OPTIONS
 --ignore-missing::
 	Ignores missing files during a --refresh
 
+--cacheinfo <mode>,<object>,<path>::
 --cacheinfo <mode> <object> <path>::
-	Directly insert the specified info into the index.
+	Directly insert the specified info into the index.  For
+	backward compatibility, you can also give these three
+	arguments as three separate parameters, but new users are
+	encouraged to use a single-parameter form.
 
 --index-info::
         Read index information from stdin.

builtin/update-index.c

@@ -629,14 +629,42 @@ static int resolve_undo_clear_callback(const struct option *opt,
 	return 0;
 }
 
+static int parse_new_style_cacheinfo(const char *arg,
+				     unsigned int *mode,
+				     unsigned char sha1[],
+				     const char **path)
+{
+	unsigned long ul;
+	char *endp;
+
+	errno = 0;
+	ul = strtoul(arg, &endp, 8);
+	if (errno || endp == arg || *endp != ',' || (unsigned int) ul != ul)
+		return -1; /* not a new-style cacheinfo */
+	*mode = ul;
+	endp++;
+	if (get_sha1_hex(endp, sha1) || endp[40] != ',')
+		return -1;
+	*path = endp + 41;
+	return 0;
+}
+
 static int cacheinfo_callback(struct parse_opt_ctx_t *ctx,
 				const struct option *opt, int unset)
 {
 	unsigned char sha1[20];
 	unsigned int mode;
+	const char *path;
 
+	if (!parse_new_style_cacheinfo(ctx->argv[1], &mode, sha1, &path)) {
+		if (add_cacheinfo(mode, sha1, path, 0))
+			die("git update-index: --cacheinfo cannot add %s", path);
+		ctx->argv++;
+		ctx->argc--;
+		return 0;
+	}
 	if (ctx->argc <= 3)
-		return error("option 'cacheinfo' expects three arguments");
+		return error("option 'cacheinfo' expects <mode>,<sha1>,<path>");
 	if (strtoul_ui(*++ctx->argv, 8, &mode) ||
 	    get_sha1_hex(*++ctx->argv, sha1) ||
 	    add_cacheinfo(mode, sha1, *++ctx->argv, 0))
@@ -740,9 +768,9 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 			PARSE_OPT_NOARG | PARSE_OPT_NONEG,
 			really_refresh_callback},
 		{OPTION_LOWLEVEL_CALLBACK, 0, "cacheinfo", NULL,
-			N_("<mode> <object> <path>"),
+			N_("<mode>,<object>,<path>"),
 			N_("add the specified entry to the index"),
-			PARSE_OPT_NOARG |	/* disallow --cacheinfo=<mode> form */
+			PARSE_OPT_NOARG | /* disallow --cacheinfo=<mode> form */
 			PARSE_OPT_NONEG | PARSE_OPT_LITERAL_ARGHELP,
 			(parse_opt_cb *) cacheinfo_callback},
 		{OPTION_CALLBACK, 0, "chmod", &set_executable_bit, N_("(+/-)x"),

t/t2107-update-index-basic.sh

@@ -48,4 +48,17 @@ test_expect_success '--cacheinfo does not accept gitlink null sha1' '
 	test_cmp expect actual
 '
 
+test_expect_success '--cacheinfo mode,sha1,path (new syntax)' '
+	echo content >file &&
+	git hash-object -w --stdin <file >expect &&
+
+	git update-index --add --cacheinfo 100644 "$(cat expect)" file &&
+	git rev-parse :file >actual &&
+	test_cmp expect actual &&
+
+	git update-index --add --cacheinfo "100644,$(cat expect),elif" &&
+	git rev-parse :elif >actual &&
+	test_cmp expect actual
+'
+
 test_done