you-still-use-that??: help deprecating commands for removal

Commands slated for removal like "git pack-redundant" now require
an explicit "--i-still-use-this" option to run.  This is to
discourage casual use and surface their pending deprecation to
users.

The warning message is long, so factor it into a helper function
you_still_use_that() to simplify reuse by other commands.

Also add a missing test to ensure this enforcement works for
"pack-redundant".

Helped-by: Elijah Newren <[email protected]>
[en: log message]
Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

builtin/pack-redundant.c

@@ -625,14 +625,8 @@ int cmd_pack_redundant(int argc, const char **argv, const char *prefix UNUSED, s
 			break;
 	}
 
-	if (!i_still_use_this) {
-		fputs(_("'git pack-redundant' is nominated for removal.\n"
-			"If you still use this command, please add an extra\n"
-			"option, '--i-still-use-this', on the command line\n"
-			"and let us know you still use it by sending an e-mail\n"
-			"to <[email protected]>.  Thanks.\n"), stderr);
-		die(_("refusing to run without --i-still-use-this"));
-	}
+	if (!i_still_use_this)
+		you_still_use_that("git pack-redundant");
 
 	if (load_all_packs)
 		load_all();

git-compat-util.h

@@ -703,6 +703,8 @@ void warning_errno(const char *err, ...) __attribute__((format (printf, 1, 2)));
 
 void show_usage_if_asked(int ac, const char **av, const char *err);
 
+NORETURN void you_still_use_that(const char *command_name);
+
 #ifndef NO_OPENSSL
 #ifdef APPLE_COMMON_CRYPTO
 #include "compat/apple-common-crypto.h"

t/t5323-pack-redundant.sh

@@ -45,6 +45,11 @@ fi
 main_repo=main.git
 shared_repo=shared.git
 
+test_expect_success 'pack-redundant needs --i-still-use-this' '
+	test_must_fail git pack-redundant >message 2>&1 &&
+	test_grep "nominated for removal" message
+'
+
 git_pack_redundant='git pack-redundant --i-still-use-this'
 
 # Create commits in <repo> and assign each commit's oid to shell variables

usage.c

@@ -372,3 +372,15 @@ void bug_fl(const char *file, int line, const char *fmt, ...)
 	trace2_cmd_error_va(fmt, ap);
 	va_end(ap);
 }
+
+NORETURN void you_still_use_that(const char *command_name)
+{
+	fprintf(stderr,
+		_("'%s' is nominated for removal.\n"
+		  "If you still use this command, please add an extra\n"
+		  "option, '--i-still-use-this', on the command line\n"
+		  "and let us know you still use it by sending an e-mail\n"
+		  "to <[email protected]>.  Thanks.\n"),
+		command_name);
+	die(_("refusing to run without --i-still-use-this"));
+}