~sircmpwn/aerc

ref: 0.2.1 aerc/worker d---------
Fix error handling in maildir worker
Register worker in init.

This allows backends which can't always be compiled due to missing
dependencies (say libnotmuch) to be compiled conditionally with buildflags.
maildir: Watch for new messages

When a directory is opened, start watching its "new" subdirectory for
incoming messages using the fsnotify library. When creation events are
detected, run the Unseen routine to move the message from new to cur and
add new UIDs to the store, updating the UI's list of directory contents
as we go.
Fix header decoding

Email headers can be encoded with different charsets, which is signalled
using a special character sequence. The go-message package provides two
different methods for accessing header values, Get(key) (actually
inherited from the embedded textproto.Header) which returns the raw
header value and Text(key), which returns the header's value decoded as
UTF-8.

Before, in the maildir backend, we were using the Get method which
sometimes resulted in encoded headers being displayed in the UI. This
patch replaces the incorrect usage of Get() with Text().
Fix missing format fields in maildir/container.go
Implement maildir copy

Create a delivery in the destination directory with the content of the
source message.
Add maildir backend worker

Add the initial implementation of a backend for Maildir accounts. Much
of the functionality required is implemented in the go-message and
go-maildir libraries, so we use them as much as possible.

The maildir worker hooks into a new maildir:// URL scheme in the
accounts.conf file which points to a container of several maildir
directories. From there, the OpenDirectory, FetchDirectoryContents, etc
messages work on subdirectories. This is implemented as a Container
struct which handles mapping between the symbolic email folder names and
UIDs to the concrete directories and file names.
#190 Handle gmail duplicate folder
Support imaps with oauthbearer authentication (Gmail)

    imaps+oauthbearer://user:token@host?token_endpoint=...

 - the config Source password is used as access token if
   no token_endpoint parameter is set
 - the config Source password is used as refresh token if
   token_endpoint parameter is set, and used to exchange
   with an access token

The implementation has only been tested with Gmail.

    source = imaps+oauthbearer://{username}:{refersh_token}@imap.gmail.com:993? \
    client_id=XX&\
    client_secret=XX&\
    token_endpoint=https%3A%2F%2Faccounts.google.com%2Fo%2Foauth2%2Ftoken

client credentials created with

    https://console.developers.google.com/apis/credentials

refresh token created with

    https://github.com/google/gmail-oauth2-tools/blob/master/python/oauth2.py

rel: https://todo.sr.ht/~sircmpwn/aerc2/42
Factor IMAP-specific structs out of UI models

Before, we were using several IMAP-specific concepts to represent
information being displayed in the UI. Factor these structures out of
the IMAP package to make it easier for other backends to provide the
required information.
Use []uint32 instead of imap.SeqSet

A sequence-set is an IMAP-specific implementation detail. Throughout the
UI, aerc simply operates using lists of opaque identifiers. In order to
loosen the coupling between the UI and IMAP in particular, replace most
usages of imap.SeqSet with []uint32, leaving the translation to a SeqSet
to the IMAP backend as needed.
Factor UI models out of the worker message package

Before, the information needed to display different parts of the UI was
tightly coupled to the specific messages being sent back and forth to
the backend worker. Separating out a models package allows us to be more
specific about exactly what a backend is able to and required to
provide for the UI.
Sort out dirstore once and for all
worker/imap: rig up search directory handler
worker/imap: implement search
imap: block until directory list is fully received

This fixes issues with INBOX mysteriously not being present at times
imap: respect the folder config option
Add :read and :unread commands
Update our message flags when server updates them
Add archive command

Adds an archive command that moves the current message into the folder
specified in the account config entry.

Supports three layouts at this point:

- flat: puts all messages next to each other
- year: creates a folder per year
- month: same as above, plus folders per month

This also adds a "-p" argument to "cp" and "mv" that works like
"--parents" on mkdir(1). We use this to auto-create the directories
for the archive layout.
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