piem-inboxes: Support mapping inbox to multiple coderepos

An inbox may regularly receive patches for multiple repos.  Allow an
inbox's :coderepo to be a list, and teach piem-inbox-coderepo to
select a target repo by prompting the caller with the configured list.

Message-Id: <20220506014017.14259-1-kyle@kyleam.com>

4 files changed, 64 insertions, 20 deletions

diff --git a/Documentation/piem.texi b/Documentation/piem.texi
index fc9f795..26962a4 100644
--- a/Documentation/piem.texi
+++ b/Documentation/piem.texi
@@ -163,7 +163,10 @@ buffer can be mapped to an inbox in @code{piem-inboxes}.
 that contains code related to that archive (in the example above, a
 local clone of @url{https://git.kernel.org/pub/scm/git/git.git/}).  This
 information is required to apply patches from an archive to a local code
-repository (@pxref{Applying patches}).
+repository (@pxref{Applying patches}).  To map an inbox to more than one
+repository (e.g., if the inbox receives patches for multiple projects,
+or if you use a few dedicated Git worktrees for different types of
+patches), set @code{:coderepo} to a list of locations.
 
 @findex piem-merged-inboxes
 @vindex piem-get-inboxes-from-config
diff --git a/TODO b/TODO
index 97d2d7f..e6a90ea 100644
--- a/TODO
+++ b/TODO
@@ -2,10 +2,6 @@ A (sparse and likely stale) to-do list for piem                   -*-outline-*-
 
 * general
 
-** piem-inboxes: support mapping inbox to multiple coderepos
-A catchall inbox may be used for small projects without a dedicated
-address.
-
 ** "report inbox" command for debugging
 
 ** "show message ID at point" command
diff --git a/piem.el b/piem.el
index 22d8212..f91e3e6 100644
--- a/piem.el
+++ b/piem.el
@@ -58,10 +58,6 @@
   :link '(info-link "(piem)Top")
   :group 'tools)
 
-;; TODO: Decide how to deal with inboxes that map to more than one
-;; coderepo.  This is important to support for people that want to
-;; use a catchall inbox for small projects which they don't think
-;; (yet) need a dedicated address.
 (defcustom piem-inboxes nil
   "List of public-inbox-archived projects.
 
@@ -77,6 +73,12 @@ list that supports the following properties:
       differs from public-inbox-config's coderepo, which is a link to
       another section that must point to the repository's git
       directory.
+
+      To map an inbox to multiple repositories, you can set this
+      to a list of strings.  When a function (e.g., `piem-am')
+      needs a single coderepo, you will be prompted to select a
+      repository, with the first value in this list offered as
+      the default.
   :url
       A URL hosting HTTPS archives.  This value must end with a slash.
   :maildir
@@ -100,8 +102,7 @@ configuration are considered."
   ;; `piem--merge-config-inboxes' so that the value can also be set in
   ;; ~/.public-inbox/config.
   :type '(alist :key-type string
-                :value-type
-                (plist :value-type string))
+                :value-type plist)
   :set (lambda (var val)
          (set var val)
          (when (fboundp 'piem-clear-merged-inboxes)
@@ -398,16 +399,23 @@ files."
              (let* ((inbox-name (match-string 1 key))
                     (inbox-item (assoc inbox-name cfg-inboxes))
                     (prop-name (intern (concat ":" (match-string 2 key))))
-                    (prop-pair (list prop-name (car val))))
-               (when-let ((coderepo
+                    (prop-pair (list prop-name
+                                     (if (eq prop-name :coderepo)
+                                         val
+                                       (car val)))))
+               (when-let ((coderepos
                            (and (eq prop-name :coderepo)
-                                (car (gethash
-                                      (format "coderepo.%s.dir" (car val))
-                                      pi-cfg)))))
+                                (mapcar
+                                 (lambda (v)
+                                   (car (gethash (format "coderepo.%s.dir" v)
+                                                 pi-cfg)))
+                                 val))))
                  (setq prop-pair
                        (list :coderepo
-                             (replace-regexp-in-string
-                              "/\\.git/?\\'" "" coderepo))))
+                             (mapcar
+                              (lambda (r)
+                                (replace-regexp-in-string "/\\.git/?\\'" "" r))
+                              coderepos))))
                (if inbox-item
                    (setcdr inbox-item (nconc prop-pair (cdr inbox-item)))
                  (push (cons inbox-name prop-pair) cfg-inboxes)))))
@@ -516,8 +524,16 @@ returned by `piem-inbox'."
 
 (defun piem-inbox-coderepo (&optional inbox)
   "Return the code repository of current buffer's inbox."
-  (when-let ((repo (piem-inbox-get :coderepo inbox)))
-    (file-name-as-directory (expand-file-name repo))))
+  (when-let ((inbox (or inbox (piem-inbox)))
+             (repos (piem-inbox-get :coderepo inbox)))
+    (when (stringp repos)
+      (setq repos (list repos)))
+    (let ((repo (if (= (length repos) 1)
+                    (car repos)
+                  (completing-read "Code repository: " repos
+                                   nil t nil nil (car repos)))))
+      (unless (string-blank-p repo)
+        (file-name-as-directory (expand-file-name repo))))))
 
 (defun piem-inbox-maildir-directory (&optional inbox)
   "Return the maildir for INBOX.
diff --git a/tests/piem-tests.el b/tests/piem-tests.el
index 444ed5f..79d8591 100644
--- a/tests/piem-tests.el
+++ b/tests/piem-tests.el
@@ -49,6 +49,21 @@
           dir = /code/foo/.git
 ")
 
+(defvar piem-tests-sample-pi-config-multiple-coderepos "
+[publicinbox \"foo\"]
+        address = foo@example.com
+        url = https://example.com/foo
+        inboxdir = /inboxes/foo
+        coderepo = foo.git
+        coderepo = bar.git
+
+[coderepo \"foo.git\"]
+          dir = /code/foo/.git
+
+[coderepo \"bar.git\"]
+          dir = /code/bar/.git
+")
+
 (ert-deftest piem-merged-inboxes:from-config-disabled ()
   (let ((piem-get-inboxes-from-config nil)
         (piem-inboxes nil))
@@ -78,6 +93,20 @@
       (piem-clear-merged-inboxes)
       (should-not (piem-inbox-get :address "foo")))))
 
+(ert-deftest piem-merged-inboxes:from-config-multiple-coderepos ()
+  (piem-clear-merged-inboxes)
+  (let ((piem-get-inboxes-from-config t)
+        (piem-inboxes nil))
+    (piem-tests-with-pi-config piem-tests-sample-pi-config-multiple-coderepos
+      (cl-letf (((symbol-function 'completing-read)
+                 (lambda (&rest _) "/code/foo")))
+        (should (equal (piem-inbox-coderepo "foo")
+                       "/code/foo/")))
+      (cl-letf (((symbol-function 'completing-read)
+                 (lambda (&rest _) "/code/bar")))
+        (should (equal (piem-inbox-coderepo "foo")
+                       "/code/bar/"))))))
+
 (ert-deftest piem-merged-inboxes:override-config ()
   (piem-clear-merged-inboxes)
   (let ((piem-get-inboxes-from-config t)