Merge branch 'km/am-create-worktree'

3 files changed, 87 insertions, 22 deletions

diff --git a/piem-b4.el b/piem-b4.el
index 27ecf19..172236f 100644
--- a/piem-b4.el
+++ b/piem-b4.el
@@ -130,15 +130,21 @@ list of arguments specified via ARGS."
          (append args (list mid))))
 
 ;;;###autoload
-(defun piem-b4-am-from-mid (mid &optional args)
+(defun piem-b4-am-from-mid (mid &optional args toggle-worktree)
   "Get the thread for MID, extract an am-ready mbox, and apply it.
+
 Try to get a thread for the Message-Id MID with
 `piem-mid-to-thread-functions', falling back to letting b4
 download it.  After calling `b4 am' with ARGS to prepare an
-am-ready mbox, feed the result to `git am'."
+am-ready mbox, feed the result to `git am'.
+
+When prefix argument TOGGLE-WORKTREE is non-nil, invert the
+meaning of `piem-am-create-worktree'.  With the default value,
+this triggers the creation of a new worktree."
   (interactive (list (or (piem-mid)
                          (read-string "Message ID: "))
-                     (transient-args 'piem-b4-am)))
+                     (transient-args 'piem-b4-am)
+                     current-prefix-arg))
   (when-let ((badopt (cl-some
                       (lambda (arg)
                         (and (string-match
@@ -158,7 +164,8 @@ am-ready mbox, feed the result to `git am'."
                  (with-temp-buffer
                    (insert-file-contents (or cover mbox-file))
                    (piem-extract-mbox-info))
-                 coderepo)
+                 coderepo
+                 toggle-worktree)
       (when clean-fn
         (funcall clean-fn)))))
 
diff --git a/piem.el b/piem.el
index 5ad2b94..784d0b3 100644
--- a/piem.el
+++ b/piem.el
@@ -154,6 +154,18 @@ the following information about the patch series:
       The reported base commit of the patch, if any."
   :type 'function)
 
+(defcustom piem-am-create-worktree nil
+  "Whether to create a dedicated worktree for applying patches."
+  :type 'boolean)
+
+(defcustom piem-am-read-worktree-function #'piem-am-read-worktree
+  "Function that reads a to-be-created worktree from the user.
+This function is called with two arguments, the directory of the
+code repository that the worktree will be created from and the
+name of the branch that will be created.  The branch may be nil
+if the caller requested a detached HEAD."
+  :type 'function)
+
 (defcustom piem-maildir-directory nil
   "Inject public-inbox threads into this directory.
 If non-nil, this must be an existing Maildir directory."
@@ -636,8 +648,22 @@ in `piem-default-branch-function'."
 
 (defvar piem-am-args (list "--scissors" "--3way"))
 
+(defun piem-am-read-worktree (coderepo branch)
+  "Read a worktree to create for applying patches.
+This function is intended to be used as a value of
+`piem-am-read-worktree-function'.  The worktree directory is
+completed from the parent directory of CODEREPO.  If BRANCH is
+non-nil, it is used to construct the default completion value."
+  (let ((fname (directory-file-name coderepo)))
+    (read-directory-name
+     "Create worktree: "
+     (file-name-directory fname) nil nil
+     (and branch
+          (concat (file-name-nondirectory fname) "-"
+                  (replace-regexp-in-string "/" "-" branch))))))
+
 ;;;###autoload
-(defun piem-am (mbox &optional format info coderepo)
+(defun piem-am (mbox &optional format info coderepo toggle-worktree)
   "Feed an am-ready mbox to `git am'.
 
 MBOX is a buffer whose contents are an am-ready mbox (obtained
@@ -650,8 +676,12 @@ INFO is a plist that with information to help choose a default
 branch name or starting point (see `piem-default-branch-function'
 for a list of possible properties).
 
-If CODEREPO is given, switch to this directory before calling
-`git am'."
+CODEREPO, if given, indicates the code repository to operate
+within.  If not specified, the default directory is used.
+
+When prefix argument TOGGLE-WORKTREE is non-nil, invert the
+meaning of `piem-am-create-worktree'.  With the default value,
+this triggers the creation of a new worktree."
   (interactive
    (pcase-let ((`(,mbox . ,format)
                 (or (piem-am-ready-mbox)
@@ -663,15 +693,19 @@ If CODEREPO is given, switch to this directory before calling
      (list (cons :interactive mbox)
            format
            (piem-extract-mbox-info mbox)
-           (piem-inbox-coderepo-maybe-read))))
+           (piem-inbox-coderepo-maybe-read)
+           current-prefix-arg)))
   (setq format (or format "mboxrd"))
-  (let ((default-directory (or coderepo default-directory))
-        (interactivep (eq (car-safe mbox) :interactive)))
+  (let* ((default-directory (or coderepo default-directory))
+         (am-directory default-directory)
+         (use-worktree (xor piem-am-create-worktree toggle-worktree))
+         (interactivep (eq (car-safe mbox) :interactive)))
     (when interactivep
       (setq mbox (cdr mbox)))
-    (let ((new-branch (read-string
-                       "New branch (empty for detached): "
-                       (funcall piem-default-branch-function info)))
+    (let ((new-branch
+           (let ((b (read-string "New branch (empty for detached): "
+                                 (funcall piem-default-branch-function info))))
+             (and (not (string-empty-p b)) b)))
           (base (completing-read
                  "Base commit: "
                  (let ((cands (and piem-use-magit
@@ -679,10 +713,19 @@ If CODEREPO is given, switch to this directory before calling
                                    (magit-list-local-branch-names)))
                        (base (plist-get info :base-commit)))
                    (if base (cons base cands) cands)))))
-      (apply #'piem-process-call nil piem-git-executable "checkout"
-             (append (if (string-empty-p new-branch)
-                         (list "--detach")
-                       (list "-b" new-branch))
+      (when use-worktree
+        (setq am-directory
+              (expand-file-name
+               (funcall piem-am-read-worktree-function
+                        default-directory new-branch)))
+        (when (file-exists-p am-directory)
+          (user-error "Worktree directory already exists")))
+      (apply #'piem-process-call nil piem-git-executable
+             (append (if use-worktree
+                         (list "worktree" "add")
+                       (list "checkout"))
+                     (if new-branch (list "-b" new-branch) (list "--detach"))
+                     (and use-worktree (list am-directory))
                      (and (not (string-blank-p base))
                           (list base)))))
     (let ((args (cons (concat "--patch-format=" format)
@@ -690,15 +733,15 @@ If CODEREPO is given, switch to this directory before calling
       (if (bufferp mbox)
           (unwind-protect
               (apply #'piem-process-call-with-buffer-input
-                     nil mbox piem-git-executable "am" args)
+                     am-directory mbox piem-git-executable "am" args)
             (when interactivep
               (kill-buffer mbox)))
-        (apply #'piem-process-call nil piem-git-executable "am"
+        (apply #'piem-process-call am-directory piem-git-executable "am"
                (append args (list mbox)))))
     (if (and piem-use-magit
              (fboundp 'magit-status-setup-buffer))
-        (magit-status-setup-buffer)
-      (dired "."))))
+        (magit-status-setup-buffer am-directory)
+      (dired am-directory))))
 
 ;;;###autoload (autoload 'piem-dispatch "piem" nil t)
 (define-transient-command piem-dispatch ()
diff --git a/piem.texi b/piem.texi
index cf39fe8..852d054 100644
--- a/piem.texi
+++ b/piem.texi
@@ -251,6 +251,17 @@ branch.  If the sender specified a base commit for the series, that will
 be provided as the default completion candidate.  Entering an empty base
 signals to use the current branch of the repository as the base.
 
+@vindex piem-am-create-worktree
+@vindex piem-am-read-worktree-function
+Rather than applying the patches directly to the associated code
+repository, you can create a dedicated worktree by setting
+@code{piem-am-create-worktree} to a non-nil value.  Giving a prefix
+argument to @code{piem-am} inverts the meaning of
+@code{piem-am-create-worktree}; that is, by default a prefix argument is
+useful if you generally prefer to work within the configured code
+repository but would like to trigger the one-off creation of a worktree
+for a particular call.
+
 @cindex magit
 @vindex piem-use-magit
 When piem loads, it detects whether Magit is loaded and sets
@@ -314,13 +325,17 @@ for more information on using Transient.)
 @itemx M-x piem-b4-am-from-mid
 @findex piem-b4-am-from-mid
 @findex piem-mid
+@vindex piem-am-create-worktree
+@vindex piem-am-read-worktree-function
 Generate or download a thread's mbox for the current buffer's message
 ID, process it into an am-ready mbox with b4, and then feed it to
 @code{git am} called within an associated Git repository.  If a message
 ID of the current buffer is not known (i.e. @code{piem-mid} returns
 nil), one is read from the caller.  The caller is also queried for the
 branch name and base, as described for @code{piem-am} (@pxref{Applying
-patches contained in a message}).
+patches contained in a message}).  And, as with @code{piem-am}, a
+worktree can be created by configuring @code{piem-am-create-worktree} to
+a non-nil value or by giving a prefix argument.
 
 @findex piem-mid-to-thread-functions
 To generate the input thread, first any functions in