rebase: deprecate --rebase-merges=""

The unusual syntax --rebase-merges="" (that is, --rebase-merges with an
empty string argument) has been an undocumented synonym of
--rebase-merges without an argument. Deprecate that syntax to avoid
confusion when a rebase.rebaseMerges config option is introduced, where
rebase.rebaseMerges="" will be equivalent to --no-rebase-merges.

It is not likely that anyone is actually using this syntax, but just in
case, deprecate the empty string argument instead of dropping support
for it immediately.

Signed-off-by: Alex Henrie <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: alexhenrie

builtin/rebase.c

@@ -1141,7 +1141,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		{OPTION_STRING, 'r', "rebase-merges", &rebase_merges,
 			N_("mode"),
 			N_("try to rebase merges instead of skipping them"),
-			PARSE_OPT_OPTARG, NULL, (intptr_t)""},
+			PARSE_OPT_OPTARG, NULL, (intptr_t)"no-rebase-cousins"},
 		OPT_BOOL(0, "fork-point", &options.fork_point,
 			 N_("use 'merge-base --fork-point' to refine upstream")),
 		OPT_STRING('s', "strategy", &options.strategy,
@@ -1439,7 +1439,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 	if (rebase_merges) {
 		if (!*rebase_merges)
-			; /* default mode; do nothing */
+			warning(_("--rebase-merges with an empty string "
+				  "argument is deprecated and will stop "
+				  "working in a future version of Git. Use "
+				  "--rebase-merges without an argument "
+				  "instead, which does the same thing."));
 		else if (!strcmp("rebase-cousins", rebase_merges))
 			options.rebase_cousins = 1;
 		else if (strcmp("no-rebase-cousins", rebase_merges))