am: shorten ident_split variable name in get_commit_info()

The local ident_split variable is often mentioned three
times per line when dealing with its begin/end pointer
pairs. Let's use a shorter name which lets us get rid of
some long lines.  Since this is a short self-contained
function, readability doesn't suffer.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/am.c

@@ -1378,33 +1378,31 @@ static void get_commit_info(struct am_state *state, struct commit *commit)
 {
 	const char *buffer, *ident_line, *msg;
 	size_t ident_len;
-	struct ident_split ident_split;
+	struct ident_split id;
 
 	buffer = logmsg_reencode(commit, NULL, get_commit_output_encoding());
 
 	ident_line = find_commit_header(buffer, "author", &ident_len);
 
-	if (split_ident_line(&ident_split, ident_line, ident_len) < 0)
+	if (split_ident_line(&id, ident_line, ident_len) < 0)
 		die(_("invalid ident line: %.*s"), (int)ident_len, ident_line);
 
 	assert(!state->author_name);
-	if (ident_split.name_begin) {
+	if (id.name_begin)
 		state->author_name =
-			xmemdupz(ident_split.name_begin,
-				 ident_split.name_end - ident_split.name_begin);
-	} else
+			xmemdupz(id.name_begin, id.name_end - id.name_begin);
+	else
 		state->author_name = xstrdup("");
 
 	assert(!state->author_email);
-	if (ident_split.mail_begin) {
+	if (id.mail_begin)
 		state->author_email =
-			xmemdupz(ident_split.mail_begin,
-				 ident_split.mail_end - ident_split.mail_begin);
-	} else
+			xmemdupz(id.mail_begin, id.mail_end - id.mail_begin);
+	else
 		state->author_email = xstrdup("");
 
 	assert(!state->author_date);
-	state->author_date = xstrdup(show_ident_date(&ident_split, DATE_MODE(NORMAL)));
+	state->author_date = xstrdup(show_ident_date(&id, DATE_MODE(NORMAL)));
 
 	assert(!state->msg);
 	msg = strstr(buffer, "\n\n");