[elpa] externals/dtache 8d4106e2f2: Monitor updates to the database

[ELPA Syncer]

branch: externals/dtache
commit 8d4106e2f2b352e1b4d9585b888547414df9318c
Author: Niklas Eklund <niklas.eklund@posteo.net>
Commit: Niklas Eklund <niklas.eklund@posteo.net>

    Monitor updates to the database
    
    This patch utilizes filenotify to add a watch for the
    dtache-db-directory. This is needed in order for dtache to support
    multiple active Emacs sessions. Any change to the database by any of
    the Emacs instances will trigger a re-initialization of all
    dtache-sessions. This means that once a session is created from any of
    the Emacs sessions, that information will propagate to the others as well.
---
 CHANGELOG.org |  2 ++
 dtache.el     | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/CHANGELOG.org b/CHANGELOG.org
index 093afe3058..8f3e31f60f 100644
--- a/CHANGELOG.org
+++ b/CHANGELOG.org
@@ -4,6 +4,8 @@
 
 * Development
 
+- Support for multiple Emacs sessions. When a =dtache= session is created, it 
will now become visible in all active Emacs sessions.
+
 * Version 0.4 (2022-010-22)
 
 - =dtache= takes care of setting up the keybindings for its users. The detach 
key can be customized through =dtache-detach-key=
diff --git a/dtache.el b/dtache.el
index 48bd6443a1..e627ab17d9 100644
--- a/dtache.el
+++ b/dtache.el
@@ -214,6 +214,8 @@ This version is encoded as [package-version].[revision].")
   "A list of sessions.")
 (defvar dtache--watched-session-directories nil
   "An alist where values are a (directory . descriptor).")
+(defvar dtache--db-watch nil
+  "A descriptor to the `dtache-db-directory'.")
 (defvar dtache--buffer-session nil
   "The `dtache-session' session in current buffer.")
 (defvar dtache--current-session nil
@@ -598,6 +600,11 @@ Optionally SUPPRESS-OUTPUT."
     (unless (file-exists-p dtache-db-directory)
       (make-directory dtache-db-directory t))
     (dtache--db-initialize)
+    (setq dtache--db-watch
+      (file-notify-add-watch dtache-db-directory
+                             '(change attribute-change)
+                             #'dtache--db-directory-event))
+    (setq dtache--sessions-initialized t)
 
     ;; Remove missing local sessions
     (thread-last (dtache--db-get-sessions)
@@ -1129,6 +1136,16 @@ session and trigger a state transition."
           (setq dtache--watched-session-directories
                 (assoc-delete-all session-directory 
dtache--watched-session-directories)))))))
 
+(defun dtache--db-directory-event (event)
+  "Act on EVENT in `dtache-db-directory'.
+
+If event is cased by an update to the `dtache' database, re-initialize
+`dtache--sessions'."
+  (pcase-let ((`(,_descriptor ,action ,file)))
+    (when (and (string= "dtache.db" file)
+               (eq 'attribute-changed action)))
+    (dtache--db-initialize)))
+
 ;;;;; UI
 
 (defun dtache--metadata-str (session)