rebase: make builtin and legacy script error messages the same

The conversion of the script version of rebase took messages that were
prefixed with "error:" and passed them along to die(), which adds a
"fatal:" prefix, thus resulting in messages of the form:

  fatal: error: cannot combine...

which seems redundant.  Remove the "error:" prefix from the builtin
version of rebase, and change the prefix from "error:" to "fatal:" in
the legacy script to match.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: newren

builtin/rebase.c

@@ -1223,12 +1223,12 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 				break;
 
 		if (is_interactive(&options) && i >= 0)
-			die(_("error: cannot combine interactive options "
+			die(_("cannot combine interactive options "
 			      "(--interactive, --exec, --rebase-merges, "
 			      "--preserve-merges, --keep-empty, --root + "
 			      "--onto) with am options (%s)"), buf.buf);
 		if (options.type == REBASE_MERGE && i >= 0)
-			die(_("error: cannot combine merge options (--merge, "
+			die(_("cannot combine merge options (--merge, "
 			      "--strategy, --strategy-option) with am options "
 			      "(%s)"), buf.buf);
 	}
@@ -1248,15 +1248,15 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		 *       git-rebase.txt caveats with "unless you know what you are doing"
 		 */
 		if (options.rebase_merges)
-			die(_("error: cannot combine '--preserve-merges' with "
+			die(_("cannot combine '--preserve-merges' with "
 			      "'--rebase-merges'"));
 
 	if (options.rebase_merges) {
 		if (strategy_options.nr)
-			die(_("error: cannot combine '--rebase-merges' with "
+			die(_("cannot combine '--rebase-merges' with "
 			      "'--strategy-option'"));
 		if (options.strategy)
-			die(_("error: cannot combine '--rebase-merges' with "
+			die(_("cannot combine '--rebase-merges' with "
 			      "'--strategy'"));
 	}
 

git-legacy-rebase.sh

@@ -508,21 +508,21 @@ if test -n "$git_am_opt"; then
 	then
 		if test -n "$incompatible_opts"
 		then
-			die "$(gettext "error: cannot combine interactive options (--interactive, --exec, --rebase-merges, --preserve-merges, --keep-empty, --root + --onto) with am options ($incompatible_opts)")"
+			die "$(gettext "fatal: cannot combine interactive options (--interactive, --exec, --rebase-merges, --preserve-merges, --keep-empty, --root + --onto) with am options ($incompatible_opts)")"
 		fi
 	fi
 	if test -n "$do_merge"; then
 		if test -n "$incompatible_opts"
 		then
-			die "$(gettext "error: cannot combine merge options (--merge, --strategy, --strategy-option) with am options ($incompatible_opts)")"
+			die "$(gettext "fatal: cannot combine merge options (--merge, --strategy, --strategy-option) with am options ($incompatible_opts)")"
 		fi
 	fi
 fi
 
 if test -n "$signoff"
 then
 	test -n "$preserve_merges" &&
-		die "$(gettext "error: cannot combine '--signoff' with '--preserve-merges'")"
+		die "$(gettext "fatal: cannot combine '--signoff' with '--preserve-merges'")"
 	git_am_opt="$git_am_opt $signoff"
 	force_rebase=t
 fi
@@ -533,15 +533,15 @@ then
 	# Note: incompatibility with --interactive is just a strong warning;
 	#       git-rebase.txt caveats with "unless you know what you are doing"
 	test -n "$rebase_merges" &&
-		die "$(gettext "error: cannot combine '--preserve-merges' with '--rebase-merges'")"
+		die "$(gettext "fatal: cannot combine '--preserve-merges' with '--rebase-merges'")"
 fi
 
 if test -n "$rebase_merges"
 then
 	test -n "$strategy_opts" &&
-		die "$(gettext "error: cannot combine '--rebase-merges' with '--strategy-option'")"
+		die "$(gettext "fatal: cannot combine '--rebase-merges' with '--strategy-option'")"
 	test -n "$strategy" &&
-		die "$(gettext "error: cannot combine '--rebase-merges' with '--strategy'")"
+		die "$(gettext "fatal: cannot combine '--rebase-merges' with '--strategy'")"
 fi
 
 if test -z "$rebase_root"