ident.c: treat $EMAIL as giving user.email identity explicitly

The environment variable EMAIL has been honored since 28a94f8 (Fall back
to $EMAIL for missing GIT_AUTHOR_EMAIL and GIT_COMMITTER_EMAIL,
2007-04-28) as the end-user's wish to use the address as the identity.
When we use it, we should say we are explicitly given email by the user.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

ident.c

@@ -85,10 +85,11 @@ static void setup_ident(void)
 	if (!git_default_email[0]) {
 		const char *email = getenv("EMAIL");
 
-		if (email && email[0])
+		if (email && email[0]) {
 			strlcpy(git_default_email, email,
 				sizeof(git_default_email));
-		else {
+			user_ident_explicitly_given |= IDENT_MAIL_GIVEN;
+		} else {
 			if (!pw)
 				pw = getpwuid(getuid());
 			if (!pw)