reset: reinstate support for the deprecated --stdin option

The `--stdin` option was a well-established paradigm in other commands,
therefore we implemented it in `git reset` for use by Visual Studio.

Unfortunately, upstream Git decided that it is time to introduce
`--pathspec-from-file` instead.

To keep backwards-compatibility for some grace period, we therefore
reinstate the `--stdin` option on top of the `--pathspec-from-file`
option, but mark it firmly as deprecated.

Helped-by: Victoria Dye <vdye@github.com>
Helped-by: Matthew John Cheetham <mjcheetham@outlook.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Documentation/git-reset.txt

@@ -12,6 +12,7 @@ SYNOPSIS
 'git reset' [-q] [--pathspec-from-file=<file> [--pathspec-file-nul]] [<tree-ish>]
 'git reset' (--patch | -p) [<tree-ish>] [--] [<pathspec>...]
 'git reset' [--soft | --mixed [-N] | --hard | --merge | --keep] [-q] [<commit>]
+DEPRECATED: 'git reset' [-q] [--stdin [-z]] [<tree-ish>]
 
 DESCRIPTION
 -----------
@@ -133,6 +134,16 @@ OPTIONS
 +
 For more details, see the 'pathspec' entry in linkgit:gitglossary[7].
 
+--stdin::
+	DEPRECATED (use `--pathspec-from-file=-` instead): Instead of taking
+	list of paths from the command line, read list of paths from the
+	standard input. Paths are separated by LF (i.e. one path per line) by
+	default.
+
+-z::
+	DEPRECATED (use `--pathspec-file-nul` instead): Only meaningful with
+	`--stdin`; paths are separated with NUL character instead of LF.
+
 EXAMPLES
 --------
 

builtin/reset.c

@@ -35,6 +35,8 @@
 #include "trace2.h"
 #include "dir.h"
 #include "add-interactive.h"
+#include "strbuf.h"
+#include "quote.h"
 
 #define REFRESH_INDEX_DELAY_WARNING_IN_MS (2 * 1000)
 
@@ -43,6 +45,7 @@ static const char * const git_reset_usage[] = {
 	N_("git reset [-q] [<tree-ish>] [--] <pathspec>..."),
 	N_("git reset [-q] [--pathspec-from-file [--pathspec-file-nul]] [<tree-ish>]"),
 	N_("git reset --patch [<tree-ish>] [--] [<pathspec>...]"),
+	N_("DEPRECATED: git reset [-q] [--stdin [-z]] [<tree-ish>]"),
 	NULL
 };
 
@@ -340,6 +343,7 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	struct object_id oid;
 	struct pathspec pathspec;
 	int intent_to_add = 0;
+	int nul_term_line = 0, read_from_stdin = 0;
 	const struct option options[] = {
 		OPT__QUIET(&quiet, N_("be quiet, only report errors")),
 		OPT_BOOL(0, "no-refresh", &no_refresh,
@@ -368,6 +372,10 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 				N_("record only the fact that removed paths will be added later")),
 		OPT_PATHSPEC_FROM_FILE(&pathspec_from_file),
 		OPT_PATHSPEC_FILE_NUL(&pathspec_file_nul),
+		OPT_BOOL('z', NULL, &nul_term_line,
+			N_("DEPRECATED (use --pathspec-file-nul instead): paths are separated with NUL character")),
+		OPT_BOOL(0, "stdin", &read_from_stdin,
+				N_("DEPRECATED (use --pathspec-from-file=- instead): read paths from <stdin>")),
 		OPT_END()
 	};
 
@@ -377,6 +385,14 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 						PARSE_OPT_KEEP_DASHDASH);
 	parse_args(&pathspec, argv, prefix, patch_mode, &rev);
 
+	if (read_from_stdin) {
+		warning(_("--stdin is deprecated, please use --pathspec-from-file=- instead"));
+		free(pathspec_from_file);
+		pathspec_from_file = xstrdup("-");
+		if (nul_term_line)
+			pathspec_file_nul = 1;
+	}
+
 	if (pathspec_from_file) {
 		if (patch_mode)
 			die(_("options '%s' and '%s' cannot be used together"), "--pathspec-from-file", "--patch");

t/t7108-reset-stdin.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+
+test_description='reset --stdin'
+
+. ./test-lib.sh
+
+test_expect_success 'reset --stdin' '
+	test_commit hello &&
+	git rm hello.t &&
+	test -z "$(git ls-files hello.t)" &&
+	echo hello.t | git reset --stdin &&
+	test hello.t = "$(git ls-files hello.t)"
+'
+
+test_expect_success 'reset --stdin -z' '
+	test_commit world &&
+	git rm hello.t world.t &&
+	test -z "$(git ls-files hello.t world.t)" &&
+	printf world.tQworld.tQhello.tQ | q_to_nul | git reset --stdin -z &&
+	printf "hello.t\nworld.t\n" >expect &&
+	git ls-files >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '--stdin requires --mixed' '
+	echo hello.t >list &&
+	test_must_fail git reset --soft --stdin <list &&
+	test_must_fail git reset --hard --stdin <list &&
+	git reset --mixed --stdin <list
+'
+
+test_done