Allow to overwrite the response Content-Type from options (#1134)

* Allow to override the response `Content-Type` from options

* Apply suggestions from code review

Co-authored-by: Jakub Roztocil <jakub@roztocil.co>

* Rename the option from `--response.content-type` to `--response-as`

* Update CHANGELOG.md

Co-authored-by: Jakub Roztocil <jakub@roztocil.co>

httpie/cli/argparser.py

@@ -457,7 +457,10 @@ class HTTPieArgumentParser(argparse.ArgumentParser):
             self.error('--continue requires --output to be specified')
 
     def _process_format_options(self):
+        format_options = self.args.format_options or []
+        if self.args.response_as is not None:
+            format_options.append('response.as:' + self.args.response_as)
         parsed_options = PARSED_DEFAULT_FORMAT_OPTIONS
-        for options_group in self.args.format_options or []:
+        for options_group in format_options:
             parsed_options = parse_format_options(options_group, defaults=parsed_options)
         self.args.format_options = parsed_options

httpie/cli/constants.py

@@ -85,11 +85,13 @@ PRETTY_MAP = {
 PRETTY_STDOUT_TTY_ONLY = object()
 
 
+EMPTY_FORMAT_OPTION = "''"
 DEFAULT_FORMAT_OPTIONS = [
     'headers.sort:true',
     'json.format:true',
     'json.indent:4',
     'json.sort_keys:true',
+    'response.as:' + EMPTY_FORMAT_OPTION,
     'xml.format:true',
     'xml.indent:2',
 ]

httpie/cli/definition.py

@@ -309,6 +309,20 @@ output_processing.add_argument(
     '''
 )
 
+output_processing.add_argument(
+    '--response-as',
+    metavar='CONTENT_TYPE',
+    help='''
+    Override the response Content-Type for formatting purposes, e.g.:
+
+        --response-as=application/xml
+
+    It is a shortcut for:
+
+        --format-options=response.as:CONTENT_TYPE
+    '''
+)
+
 
 output_processing.add_argument(
     '--format-options',