Clean upload.py, make platform use write_flash

Make upload.py more concise and pythonic.

Use the "write_flash" argument in platform.txt for uploads instead of
assuming anything that is a file is the bin to upload.

platform.txt

@@ -149,7 +149,7 @@ tools.esptool.upload.params.quiet=
 # First, potentially perform an erase or nothing
 # Next, do the binary upload
 # Combined in one rule because Arduino doesn't suport upload.1.pattern/upload.3.pattern
-tools.esptool.upload.pattern="{cmd}" "{runtime.platform.path}/tools/upload.py" --chip esp8266 --port "{serial.port}" --baud "{upload.speed}" "{upload.verbose}" {upload.erase_cmd} {upload.resetmethod} "{build.path}/{build.project_name}.bin"
+tools.esptool.upload.pattern="{cmd}" "{runtime.platform.path}/tools/upload.py" --chip esp8266 --port "{serial.port}" --baud "{upload.speed}" "{upload.verbose}" {upload.erase_cmd} {upload.resetmethod} write_flash 0x0 "{build.path}/{build.project_name}.bin"
 
 tools.esptool.upload.network_pattern="{network_cmd}" "{runtime.platform.path}/tools/espota.py" -i "{serial.port}" -p "{network.port}" "--auth={network.password}" -f "{build.path}/{build.project_name}.bin"
 

tools/upload.py

@@ -39,28 +39,16 @@
     # https://github.com/esp8266/Arduino/issues/6755#issuecomment-553208688
     if thisarg == "erase_flash":
         write_option = '--erase-all'
-        thisarg = ''
-
-    if thisarg == 'erase_region':
+    elif thisarg == 'erase_region':
         erase_addr = sys.argv.pop(0)
         erase_len = sys.argv.pop(0)
-        thisarg = ''
-
-    # Backwards compatibility with fs upload tools, eat --end
-    if thisarg == '--end':
-        thisarg = ''
-
-    # Backwards compatibility with fs upload tools, parse write_flash for later use
-    if thisarg == 'write_flash':
+    elif thisarg == '--end':
+        # Backwards compatibility with fs upload tools, eat --end
+        pass
+    elif thisarg == 'write_flash':
         write_addr = sys.argv.pop(0)
         binary = sys.argv.pop(0)
-        thisarg = ''
-
-    if os.path.isfile(thisarg):
-        binary = thisarg
-        thisarg = ''
-
-    if len(thisarg):
+    elif len(thisarg):
         cmdline = cmdline + [thisarg]
 
 cmdline = cmdline + ['write_flash']
@@ -70,7 +58,7 @@
 
 erase_file = ''
 if len(erase_addr):
-    # generate temporary empty (0xff) file
+    # Generate temporary empty (0xff) file
     eraser = tempfile.mkstemp()
     erase_file = eraser[1]
     os.write(eraser[0], bytearray([255] * int(erase_len, 0)))