Support case folding in git fast-import when core.ignorecase=true

When core.ignorecase=true, imported file paths will be folded to match
existing directory case.

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

fast-import.c

@@ -156,6 +156,7 @@ Format of STDIN stream:
 #include "csum-file.h"
 #include "quote.h"
 #include "exec_cmd.h"
+#include "dir.h"
 
 #define PACK_ID_BITS 16
 #define MAX_PACK_ID ((1<<PACK_ID_BITS)-1)
@@ -1461,7 +1462,7 @@ static int tree_content_set(
 
 	for (i = 0; i < t->entry_count; i++) {
 		e = t->entries[i];
-		if (e->name->str_len == n && !strncmp(p, e->name->str_dat, n)) {
+		if (e->name->str_len == n && !strncmp_icase(p, e->name->str_dat, n)) {
 			if (!slash1) {
 				if (!S_ISDIR(mode)
 						&& e->versions[1].mode == mode
@@ -1527,7 +1528,7 @@ static int tree_content_remove(
 
 	for (i = 0; i < t->entry_count; i++) {
 		e = t->entries[i];
-		if (e->name->str_len == n && !strncmp(p, e->name->str_dat, n)) {
+		if (e->name->str_len == n && !strncmp_icase(p, e->name->str_dat, n)) {
 			if (!slash1 || !S_ISDIR(e->versions[1].mode))
 				goto del_entry;
 			if (!e->tree)
@@ -1577,7 +1578,7 @@ static int tree_content_get(
 
 	for (i = 0; i < t->entry_count; i++) {
 		e = t->entries[i];
-		if (e->name->str_len == n && !strncmp(p, e->name->str_dat, n)) {
+		if (e->name->str_len == n && !strncmp_icase(p, e->name->str_dat, n)) {
 			if (!slash1) {
 				memcpy(leaf, e, sizeof(*leaf));
 				if (e->tree && is_null_sha1(e->versions[1].sha1))