my-git: allow application of message-id via b4, wire to mu4e

my-email.el

@@ -516,6 +516,10 @@ Move next if the message at point is what we have just processed."
   (interactive)
   (mu4e-headers-search (format "i:%s" (my-mu4e-kill-message-id 't))))
 
+(defun mu4e-action-git-apply-b4 (msg)
+  "Find the Message-Id in the buffer and pass to b4"
+  (interactive)
+  (my-git-fetch-and-apply-via-b4 (my-mu4e-kill-message-id 't)))
 
 (defun my-mu4e-search-from (&optional edit)
   "Find msgs from author of the message, optionally EDIT the search."
@@ -700,6 +704,7 @@ to `my-mu4e-patches' for later processing."
            (append
             '(("gapply git patches" . mu4e-action-git-apply-patch)
               ("mgit am patch" . mu4e-action-git-apply-mbox)
+              ("bb4 am patch" . mu4e-action-git-apply-b4)
               ("crun checkpatch script" . my-mu4e-action-run-check-patch)
               ("MCheck if merged" . my-mu4e-action-check-if-merged)))))
     ;; Bookmarks

my-git.el

@@ -140,6 +140,20 @@ bother asking for the git tree again (useful for bulk actions)."
             (if signoff "--signoff" "")
             (shell-quote-argument file))))))
 
+(defun my-git-fetch-and-apply-via-b4 (id)
+  "Fetch `id' via the b4 tool and apply it."
+  (interactive "sMessage-id:")
+  (with-temp-buffer
+    (call-process "b4" nil t t "am" id)
+    (goto-char 0)
+    (when (re-search-forward
+           (rx (: "git am "
+                  (group (one-or-more (not space)) ".mbx"))))
+      (let ((mbox (match-string-no-properties 1)))
+        (my-git-apply-mbox mbox t)
+        (message "applied %s" mbox)
+        (delete-file mbox)))))
+
 (defun my-git-apply-region (beg end)
   "Apply region as a patch."
   (interactive "r")