commit: fix patch hunk editing with "commit -p -m"

Don't change git environment: move the GIT_EDITOR=":" override to the
hook command subprocess, like it's already done for GIT_INDEX_FILE.

Signed-off-by: Benoit Pierre <benoit.pierre@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/run-command.c b/run-command.c
index 3914d9c..75abc47 100644
--- a/run-command.c
+++ b/run-command.c
@@ -760,13 +760,11 @@
 	return path;
 }
 
-int run_hook(const char *index_file, const char *name, ...)
+int run_hook_ve(const char *const *env, const char *name, va_list args)
 {
 	struct child_process hook;
 	struct argv_array argv = ARGV_ARRAY_INIT;
-	const char *p, *env[2];
-	char index[PATH_MAX];
-	va_list args;
+	const char *p;
 	int ret;
 
 	p = find_hook(name);
@@ -775,23 +773,45 @@
 
 	argv_array_push(&argv, p);
 
-	va_start(args, name);
 	while ((p = va_arg(args, const char *)))
 		argv_array_push(&argv, p);
-	va_end(args);
 
 	memset(&hook, 0, sizeof(hook));
 	hook.argv = argv.argv;
+	hook.env = env;
 	hook.no_stdin = 1;
 	hook.stdout_to_stderr = 1;
-	if (index_file) {
-		snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", index_file);
-		env[0] = index;
-		env[1] = NULL;
-		hook.env = env;
-	}
 
 	ret = run_command(&hook);
 	argv_array_clear(&argv);
 	return ret;
 }
+
+int run_hook_le(const char *const *env, const char *name, ...)
+{
+	va_list args;
+	int ret;
+
+	va_start(args, name);
+	ret = run_hook_ve(env, name, args);
+	va_end(args);
+
+	return ret;
+}
+
+int run_hook_with_custom_index(const char *index_file, const char *name, ...)
+{
+	const char *hook_env[3] =  { NULL };
+	char index[PATH_MAX];
+	va_list args;
+	int ret;
+
+	snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", index_file);
+	hook_env[0] = index;
+
+	va_start(args, name);
+	ret = run_hook_ve(hook_env, name, args);
+	va_end(args);
+
+	return ret;
+}