Add pipeto --format=mimepart option.

The most notable use case is piping html to a browser without extra
scripts such as those shared in #789.

alot/commands/thread.py

@@ -32,6 +32,8 @@
 from ..db.utils import extract_headers
 from ..db.utils import clear_my_address
 from ..db.utils import ensure_unique_address
+from ..db.utils import remove_cte
+from ..db.utils import string_sanitize
 from ..db.envelope import Envelope
 from ..db.attachment import Attachment
 from ..db.errors import DatabaseROError
@@ -630,7 +632,8 @@ def matches(msgt):
     (['cmd'], {'help': 'shellcommand to pipe to', 'nargs': '+'}),
     (['--all'], {'action': 'store_true', 'help': 'pass all messages'}),
     (['--format'], {'help': 'output format', 'default': 'raw',
-                    'choices': ['raw', 'decoded', 'id', 'filepath']}),
+                    'choices': [
+                        'raw', 'decoded', 'id', 'filepath', 'mimepart']}),
     (['--separately'], {'action': 'store_true',
                         'help': 'call command once for each message'}),
     (['--background'], {'action': 'store_true',
@@ -669,6 +672,7 @@ def __init__(self, cmd, all=False, separately=False, background=False,
             'decoded': message content, decoded quoted printable,
             'id': message ids, separated by newlines,
             'filepath': paths to message files on disk
+            'mimepart': only pipe the currently selected mime part
         :type format: str
         :param add_tags: add 'Tags' header to the message
         :type add_tags: bool
@@ -740,6 +744,9 @@ async def apply(self, ui):
                     bodytext = msg.get_body_text()
                     msgtext = '%s\n\n%s' % (headertext, bodytext)
                     pipestrings.append(msgtext)
+                elif self.output_format == 'mimepart':
+                    pipestrings.append(string_sanitize(remove_cte(
+                        msg.mime_part, as_string=True)))
 
         if not self.separately:
             pipestrings = [separator.join(pipestrings)]

docs/source/usage/modes/thread.rst

@@ -72,7 +72,7 @@ The following commands are available in thread mode:
 
     optional arguments
         :---all: pass all messages
-        :---format: output format; valid choices are: 'raw','decoded','id','filepath' (defaults to: 'raw')
+        :---format: output format; valid choices are: 'raw','decoded','id','filepath','mimepart' (defaults to: 'raw')
         :---separately: call command once for each message
         :---background: don't stop the interface
         :---add_tags: add 'Tags' header to the message