Fall back to $EMAIL for missing GIT_AUTHOR_EMAIL and GIT_COMMITTER_EMAIL

Some other programs get the user's email address from $EMAIL, so fall back to
that if we don't have a Git-specific email address.

Signed-off-by: Josh Triplett <josh@freedesktop.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

ident.c

@@ -195,6 +195,8 @@ const char *fmt_ident(const char *name, const char *email,
 	setup_ident();
 	if (!name)
 		name = git_default_name;
+	if (!email)
+		email = getenv("EMAIL");
 	if (!email)
 		email = git_default_email;