rerere forget: deprecate invocation without pathspec

rerere forget is a destructive command. When invoked without a path, it
operates on the current directory, potentially deleting many recorded
conflict resolutions.

To make the command safer, a path must be specified as of git 1.8.0. Until
then, give users time to write 'git rerere forget .' if they really mean
the entire current directory.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rerere.txt

@@ -7,7 +7,7 @@ git-rerere - Reuse recorded resolution of conflicted merges
 
 SYNOPSIS
 --------
-'git rerere' ['clear'|'forget' [<pathspec>]|'diff'|'status'|'gc']
+'git rerere' ['clear'|'forget' <pathspec>|'diff'|'status'|'gc']
 
 DESCRIPTION
 -----------
@@ -43,7 +43,7 @@ will automatically invoke this command.
 'forget' <pathspec>::
 
 This resets the conflict resolutions which rerere has recorded for the current
-conflict in <pathspec>.  The <pathspec> is optional.
+conflict in <pathspec>.
 
 'diff'::
 

builtin/rerere.c

@@ -8,7 +8,7 @@
 #include "xdiff-interface.h"
 
 static const char * const rerere_usage[] = {
-	"git rerere [clear | status | remaining | diff | gc]",
+	"git rerere [clear | forget path... | status | remaining | diff | gc]",
 	NULL,
 };
 
@@ -136,7 +136,10 @@ int cmd_rerere(int argc, const char **argv, const char *prefix)
 		return rerere(flags);
 
 	if (!strcmp(argv[0], "forget")) {
-		const char **pathspec = get_pathspec(prefix, argv + 1);
+		const char **pathspec;
+		if (argc < 2)
+			warning("'git rerere forget' without paths is deprecated");
+		pathspec = get_pathspec(prefix, argv + 1);
 		return rerere_forget(pathspec);
 	}