Check whether Win 7 bootmgfw.efi exists at all

Three bugs:
* Bash [ -a ] and [ ! -a ] are two different operations: the first checks for file existance, the second is a binary AND operation. Replace it with -e, which is consistent.
* Mount ISO before checking its contents
* Ensure that we extract the latest version of the wim/esd file (7z always replace)

Fixes #35

windows2usb

@@ -140,9 +140,9 @@ function get_dev_partition_num() {
 }
 
 function write_uefintfs() {
-    if [ -a "$dirpath/uefi-ntfs.img" ]; then
+    if [ -e "$dirpath/uefi-ntfs.img" ]; then
         cat "$dirpath/uefi-ntfs.img" > "$1"
-    elif [ -a "/usr/share/windows2usb/uefi-ntfs.img" ]; then
+    elif [ -e "/usr/share/windows2usb/uefi-ntfs.img" ]; then
         cat "/usr/share/windows2usb/uefi-ntfs.img" > "$1"
     fi
 }
@@ -174,11 +174,11 @@ function extract_bootmgfw_from_installwim() {
     # $2 - isomountpath
     # $3 - destdir
 
-    local fpath="$2/sources/install.wim"
-    [ ! -a "$fpath" ] && fpath="$2/sources/install.esd"
-
     mount -o ro "$1" "$2"
-    7z e "$fpath" -o"$3/efi/boot/" '?/Windows/Boot/EFI/bootmgfw.efi'
+    local fpath="$2/sources/install.wim"
+    [ ! -e "$fpath" ] && fpath="$2/sources/install.esd"
+
+    7z e "$fpath" -aoa -o"$3/efi/boot/" 'Windows/Boot/EFI/bootmgfw.efi' '?/Windows/Boot/EFI/bootmgfw.efi'
     umount "$2"
 }
 
@@ -349,8 +349,12 @@ then
         echo "${bold} == Extracting UEFI bootloader from install.wim ==${normal}"
         mkdir -p "$partpath/efi/boot/" || true
         extract_bootmgfw_from_installwim "$isopath" "$isomountpath" "$partpath"
-        mv "$partpath/efi/boot/bootmgfw.efi" "$partpath/efi/boot/bootx64.efi"
-        cp "$partpath/efi/boot/bootx64.efi" "$partpath/efi/boot/bootia32.efi"
+        if [ -e "$partpath/efi/boot/bootmgfw.efi" ]; then
+            mv "$partpath/efi/boot/bootmgfw.efi" "$partpath/efi/boot/bootx64.efi"
+            cp "$partpath/efi/boot/bootx64.efi" "$partpath/efi/boot/bootia32.efi"
+        else
+            echo "NOTE: your ISO file does not have UEFI bootloader, UEFI boot would be unavailable!"
+        fi
     fi
 
     echo "${bold} == Unmounting partition ==${normal}"