emacs: wrap process-lines

Initially just set the working directory, to avoid (the implicit)
call-process crashing when the default-directory points to a
non-existent location.

Use of a macro here is over-engineering for this change, but the same
change needs to be applied to several other process creation
primitives.

emacs/notmuch-address.el

@@ -217,7 +217,7 @@ requiring external commands."
       ;; harvest if necessary.
       (notmuch-address-harvest-trigger)))
    (t
-    (process-lines notmuch-address-command original))))
+    (notmuch--process-lines notmuch-address-command original))))
 
 (defun notmuch-address-expand-name ()
   (cond

emacs/notmuch-draft.el

@@ -239,7 +239,7 @@ applied to newly inserted messages)."
 (defun notmuch-draft-resume (id)
   "Resume editing of message with id ID."
   ;; Used by command `notmuch-show-resume-message'.
-  (let* ((tags (process-lines notmuch-command "search" "--output=tags"
+  (let* ((tags (notmuch--process-lines notmuch-command "search" "--output=tags"
 			      "--exclude=false" id))
 	 (draft (equal tags (notmuch-update-tags tags notmuch-draft-tags))))
     (when (or draft

emacs/notmuch-hello.el

@@ -496,7 +496,7 @@ diagonal."
 		    (widget-get widget :notmuch-search-oldest-first)))))
 
 (defun notmuch-saved-search-count (search)
-  (car (process-lines notmuch-command "count" search)))
+  (car (notmuch--process-lines notmuch-command "count" search)))
 
 (defun notmuch-hello-tags-per-line (widest)
   "Determine how many tags to show per line and how wide they
@@ -748,7 +748,7 @@ Complete list of currently available key bindings:
 		    (list (cons tag
 				(concat "tag:"
 					(notmuch-escape-boolean-term tag))))))
-	     (process-lines notmuch-command "search" "--output=tags" "*")))
+	     (notmuch--process-lines notmuch-command "search" "--output=tags" "*")))
 
 (defun notmuch-hello-insert-header ()
   "Insert the default notmuch-hello header."
@@ -786,7 +786,7 @@ Complete list of currently available key bindings:
 		   :help-echo "Refresh"
 		   (notmuch-hello-nice-number
 		    (string-to-number
-		     (car (process-lines notmuch-command "count")))))
+		     (car (notmuch--process-lines notmuch-command "count")))))
     (widget-insert " messages.\n")))
 
 (defun notmuch-hello-insert-saved-searches ()

emacs/notmuch-lib.el

@@ -860,6 +860,15 @@ You may need to restart Emacs or upgrade your notmuch package."))
       ;; `notmuch-logged-error' does not return.
       ))))
 
+(defmacro notmuch--apply-with-env (func &rest args)
+  `(let ((default-directory "~"))
+     (apply ,func ,@args)))
+
+(defun notmuch--process-lines (program &rest args)
+  "Wrap process-lines, binding DEFAULT-DIRECTORY to a safe
+default"
+  (notmuch--apply-with-env #'process-lines program args))
+
 (defun notmuch-call-notmuch--helper (destination args)
   "Helper for synchronous notmuch invocation commands.
 

emacs/notmuch-tree.el

@@ -1113,7 +1113,7 @@ the same as for the function notmuch-tree."
 				   (concat " and (" query-context ")"))))
 	 (sort-arg (if oldest-first "--sort=oldest-first" "--sort=newest-first"))
 	 (message-arg (if unthreaded "--unthreaded" "--entire-thread")))
-    (when (equal (car (process-lines notmuch-command "count" search-args)) "0")
+    (when (equal (car (notmuch--process-lines notmuch-command "count" search-args)) "0")
       (setq search-args basic-query))
     (notmuch-tag-clear-cache)
     (let ((proc (notmuch-start-notmuch

emacs/notmuch.el

@@ -940,7 +940,7 @@ See `notmuch-tag' for information on the format of TAG-CHANGES."
 PROMPT is the string to prompt with."
   (let* ((all-tags
 	  (mapcar (lambda (tag) (notmuch-escape-boolean-term tag))
-		  (process-lines notmuch-command "search" "--output=tags" "*")))
+		  (notmuch--process-lines notmuch-command "search" "--output=tags" "*")))
 	 (completions
 	  (append (list "folder:" "path:" "thread:" "id:" "date:" "from:" "to:"
 			"subject:" "attachment:")