Add `git-email-get-address-function' variable

This makes it possible for users to use their own function to get the
“to” address.  This could also be used for integration with piem.el.

* doc/git-email.org (Sending email): Add bullet point.
* git-email.el (git-email-get-to-address-function): Add variable.
(git-email--get-to-address): Add function.
(git-email--compose-email): Call the relevant function.

2 files changed, 22 insertions, 3 deletions

diff --git a/doc/git-email.org b/doc/git-email.org
index 8a8c343..84b1d23 100644
--- a/doc/git-email.org
+++ b/doc/git-email.org
@@ -94,6 +94,11 @@ You can see all the customizable variables running =M-x customize-group=
 - =git-email-get-files-functions= is a list of functions to run to get
   a list of patches to send.  The default, there is already support
   for dired, ibuffer and vc-dir.
+
+- =git-email-get-to-address-function= is a function that returns the
+  “to” address for a message.  The default function runs =git config
+  --list= to get the address, this will not work unless you are in a
+  git repository.
   
 ** Format patches
 - =git-email-format-patch-default-args= is a string of arguments to give
diff --git a/git-email.el b/git-email.el
index 7ed4e43..2c90fd3 100644
--- a/git-email.el
+++ b/git-email.el
@@ -82,6 +82,12 @@ not set, the 'to' address will be empty."
   :type '(list symbol)
   :group 'git-email)
 
+(defcustom git-email-get-to-address-function
+  'git-email--get-to-address
+  "Function to run to get the \“to\" address of a message."
+  :type 'symbol
+  :group 'git-email)
+
 (defcustom git-email-format-patch-default-args ""
   "Default arguments to give to 'git format-patch'."
   :type 'string
@@ -230,6 +236,15 @@ If the header is not found, return an empty string."
   "Remove HEADER if it is the subject."
   (not (string-equal (symbol-name (car header)) "subject")))
 
+(defun git-email--get-to-address ()
+  "Get the \"to\" address of the message.
+
+This runs \“git config --list\" in the current directory
+so might not always work."
+  (substring
+   (shell-command-to-string "git config --list | grep sendemail.to")
+   13 -1))                              ; Remove newline
+
 (defun git-email--compose-email (patch-file)
   "Given a PATCH-FILE, compose an email.
 Extracts the relevant headers and the diff from the PATCH-FILE and inserts
@@ -240,12 +255,11 @@ them into the message buffer."
 			(lambda (header)
 			  (not (string-equal (car (cdr header)) "")))
 			headers))
+         (sendemail-to (funcall git-email-get-to-address-function))
 	 ;; Get 'to' address from git.
-	 (sendemail-to
-	  (shell-command-to-string "git config --list | grep sendemail.to"))
 	 (to (if (string-equal sendemail-to "")
 		 "*** TO ADDRESS HERE ***"
-	       (substring sendemail-to 13 -1))) ; Remove newline
+	       sendemail-to))
 	 (diff (git-email--extract-diff patch-file)))
     (funcall git-email-compose-email-function to
 	     ;; Remove 'subject' header, otherwise two subject headers will be