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+;;; magit-section.el --- section functionality  -*- lexical-binding: t -*-
+
+;; Copyright (C) 2010-2018  The Magit Project Contributors
+;;
+;; You should have received a copy of the AUTHORS.md file which
+;; lists all contributors.  If not, see http://magit.vc/authors.
+
+;; Author: Jonas Bernoulli <jonas@bernoul.li>
+;; Maintainer: Jonas Bernoulli <jonas@bernoul.li>
+
+;; Magit is free software; you can redistribute it and/or modify it
+;; under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 3, or (at your option)
+;; any later version.
+;;
+;; Magit is distributed in the hope that it will be useful, but WITHOUT
+;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+;; or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+;; License for more details.
+;;
+;; You should have received a copy of the GNU General Public License
+;; along with Magit.  If not, see http://www.gnu.org/licenses.
+
+;;; Commentary:
+
+;; This library implements "sections" as used in all Magit buffers.
+;; If you have used Magit before, then you probably know what that
+;; means, otherwise think "read-only Org-Mode for Git", kinda.
+
+;;; Code:
+
+(require 'cl-lib)
+(require 'dash)
+(require 'eieio)
+
+(require 'magit-utils)
+
+(declare-function magit-maybe-make-margin-overlay "magit-margin" ())
+(declare-function magit-repository-local-get "magit-mode"
+                  (key &optional default repository))
+(declare-function magit-repository-local-set "magit-mode"
+                  (key value &optional repository))
+(defvar magit-keep-region-overlay)
+
+;;; Options
+
+(defgroup magit-section nil
+  "Expandable sections."
+  :link '(info-link "(magit)Sections")
+  :group 'magit)
+
+(defcustom magit-section-show-child-count t
+  "Whether to append the number of children to section headings.
+This only applies to sections for which doing so makes sense."
+  :package-version '(magit . "2.1.0")
+  :group 'magit-section
+  :type 'boolean)
+
+(defcustom magit-section-movement-hook
+  '(magit-hunk-set-window-start
+    magit-log-maybe-update-revision-buffer
+    magit-log-maybe-show-more-commits)
+  "Hook run by `magit-section-goto'.
+That function in turn is used by all section movement commands."
+  :package-version '(magit . "2.3.0")
+  :group 'magit-section
+  :type 'hook
+  :options '(magit-hunk-set-window-start
+             magit-status-maybe-update-revision-buffer
+             magit-status-maybe-update-blob-buffer
+             magit-log-maybe-update-revision-buffer
+             magit-log-maybe-update-blob-buffer
+             magit-log-maybe-show-more-commits))
+
+(defcustom magit-section-highlight-hook
+  '(magit-diff-highlight
+    magit-section-highlight
+    magit-section-highlight-selection)
+  "Functions used to highlight the current section.
+Each function is run with the current section as only argument
+until one of them returns non-nil."
+  :package-version '(magit . "2.1.0")
+  :group 'magit-section
+  :type 'hook
+  :options '(magit-diff-highlight
+             magit-section-highlight
+             magit-section-highlight-selection))
+
+(defcustom magit-section-unhighlight-hook
+  '(magit-diff-unhighlight)
+  "Functions used to unhighlight the previously current section.
+Each function is run with the current section as only argument
+until one of them returns non-nil.  Most sections are properly
+unhighlighted without requiring a specialized unhighlighter,
+diff-related sections being the only exception."
+  :package-version '(magit . "2.1.0")
+  :group 'magit-section
+  :type 'hook
+  :options '(magit-diff-unhighlight))
+
+(defcustom magit-section-set-visibility-hook
+  '(magit-diff-expansion-threshold
+    magit-section-cached-visibility)
+  "Hook used to set the initial visibility of a section.
+Stop at the first function that returns non-nil.  The returned
+value should be `show', `hide' or nil.  If no function returns
+non-nil, determine the visibility as usual, i.e. use the
+hardcoded section specific default (see `magit-insert-section')."
+  :package-version '(magit . "2.4.0")
+  :group 'magit-section
+  :type 'hook
+  :options '(magit-diff-expansion-threshold
+             magit-section-cached-visibility))
+
+(defcustom magit-section-cache-visibility t
+  "Whether to cache visibility of sections.
+
+Sections always retain their visibility state when they are being
+recreated during a refresh.  But if a section disappears and then
+later reappears again, then this option controls whether this is
+the case.
+
+If t, then cache the visibility of all sections.  If a list of
+section types, then only do so for matching sections.  If nil,
+then don't do so for any sections."
+  :package-version '(magit . "2.12.0")
+  :group 'magit-section
+  :type '(choice (const  :tag "Don't cache visibility" nil)
+                 (const  :tag "Cache visibility of all sections" t)
+                 (repeat :tag "Cache visibility for section types" symbol)))
+
+(defcustom magit-section-initial-visibility-alist nil
+  "Alist controlling the initial visibility of sections.
+
+Each element maps a section type or lineage to the initial
+visibility state for such sections.  The state has to be one of
+`show' or `hide', or a function that returns one of these symbols.
+A function is called with the section as the only argument.
+
+Use the command `magit-describe-section' to determine a section's
+lineage or type.  The vector in the output is the section lineage
+and the type is the first element of that vector.  Wildcards can
+be used, see `magit-section-match'.
+
+Currently this option is only used to override hardcoded defaults,
+but in the future it will also be used set the defaults."
+  :package-version '(magit . "2.12.0")
+  :group 'magit-section
+  :type '(alist :key-type (sexp :tag "Section type/lineage")
+                :value-type (choice (const hide)
+                                    (const show)
+                                    function)))
+
+(defface magit-section-highlight
+  '((((class color) (background light)) :background "grey95")
+    (((class color) (background  dark)) :background "grey20"))
+  "Face for highlighting the current section."
+  :group 'magit-faces)
+
+(defface magit-section-heading
+  '((((class color) (background light)) :foreground "DarkGoldenrod4" :weight bold)
+    (((class color) (background  dark)) :foreground "LightGoldenrod2" :weight bold))
+  "Face for section headings."
+  :group 'magit-faces)
+
+(defface magit-section-secondary-heading '((t :weight bold))
+  "Face for section headings of some secondary headings."
+  :group 'magit-faces)
+
+(defface magit-section-heading-selection
+  '((((class color) (background light)) :foreground "salmon4")
+    (((class color) (background  dark)) :foreground "LightSalmon3"))
+  "Face for selected section headings."
+  :group 'magit-faces)
+
+;;; Core
+
+(defclass magit-section ()
+  ((type     :initform nil :initarg :type)
+   (value    :initform nil :initarg :value)
+   (start    :initform nil :initarg :start)
+   (content  :initform nil)
+   (end      :initform nil)
+   (hidden   :initform nil)
+   (washer   :initform nil)
+   (process  :initform nil)
+   (parent   :initform nil :initarg :parent)
+   (children :initform nil)))
+
+(defclass magit-file-section (magit-section)
+  ((source   :initform nil)
+   (header   :initform nil)))
+
+(defclass magit-hunk-section (magit-section)
+  ((refined  :initform nil)))
+
+(defvar-local magit-root-section nil
+  "The root section in the current buffer.
+All other sections are descendants of this section.  The value
+of this variable is set by `magit-insert-section' and you should
+never modify it.")
+(put 'magit-root-section 'permanent-local t)
+
+(defun magit-current-section ()
+  "Return the section at point."
+  (or (get-text-property (point) 'magit-section) magit-root-section))
+
+(defun magit-section-ident (section)
+  "Return an unique identifier for SECTION.
+The return value has the form ((TYPE . VALUE)...)."
+  (with-slots (type value parent) section
+    (cons (cons type
+                (cond ((not (memq type '(unpulled unpushed))) value)
+                      ((string-match-p "@{upstream}" value) value)
+                      ;; Unfortunately Git chokes on "@{push}" when
+                      ;; the value of `push.default' does not allow a
+                      ;; 1:1 mapping.  Arbitrary commands may consult
+                      ;; the section value so we cannot use "@{push}".
+                      ;; But `unpushed' and `unpulled' sections should
+                      ;; keep their identity when switching branches
+                      ;; so we have to use another value here.
+                      ((string-match-p "\\`\\.\\." value) "..@{push}")
+                      (t "@{push}..")))
+          (and parent
+               (magit-section-ident parent)))))
+
+(defun magit-get-section (ident &optional root)
+  "Return the section identified by IDENT.
+IDENT has to be a list as returned by `magit-section-ident'."
+  (setq ident (reverse ident))
+  (let ((section (or root magit-root-section)))
+    (when (eq (car (pop ident))
+              (oref section type))
+      (while (and ident
+                  (setq section
+                        (--first
+                         (and (eq    (caar ident) (oref it type))
+                              (equal (cdar ident) (oref it value)))
+                         (oref section children))))
+        (pop ident))
+      section)))
+
+(defun magit-section-lineage (section)
+  "Return the lineage of SECTION.
+The return value has the form [TYPE...]."
+  (apply #'vector (mapcar #'car (magit-section-ident section))))
+
+(defvar magit-insert-section--current nil "For internal use only.")
+(defvar magit-insert-section--parent  nil "For internal use only.")
+(defvar magit-insert-section--oldroot nil "For internal use only.")
+
+;;; Commands
+;;;; Movement
+
+(defun magit-section-forward ()
+  "Move to the beginning of the next visible section."
+  (interactive)
+  (if (eobp)
+      (user-error "No next section")
+    (let ((section (magit-current-section)))
+      (if (oref section parent)
+          (let ((next (and (not (oref section hidden))
+                           (not (= (oref section end)
+                                   (1+ (point))))
+                           (car (oref section children)))))
+            (while (and section (not next))
+              (unless (setq next (car (magit-section-siblings section 'next)))
+                (setq section (oref section parent))))
+            (if next
+                (magit-section-goto next)
+              (user-error "No next section")))
+        (magit-section-goto 1)))))
+
+(defun magit-section-backward ()
+  "Move to the beginning of the current or the previous visible section.
+When point is at the beginning of a section then move to the
+beginning of the previous visible section.  Otherwise move to
+the beginning of the current section."
+  (interactive)
+  (if (bobp)
+      (user-error "No previous section")
+    (let ((section (magit-current-section)) children)
+      (cond
+       ((and (= (point)
+                (1- (oref section end)))
+             (setq children (oref section children)))
+        (magit-section-goto (car (last children))))
+       ((and (oref section parent)
+             (not (= (point)
+                     (oref section start))))
+        (magit-section-goto section))
+       (t
+        (let ((prev (car (magit-section-siblings section 'prev))))
+          (if prev
+              (while (and (not (oref prev hidden))
+                          (setq children (oref prev children)))
+                (setq prev (car (last children))))
+            (setq prev (oref section parent)))
+          (cond (prev
+                 (magit-section-goto prev))
+                ((oref section parent)
+                 (user-error "No previous section"))
+                ;; Eob special cases.
+                ((not (get-text-property (1- (point)) 'invisible))
+                 (magit-section-goto -1))
+                (t
+                 (goto-char (previous-single-property-change
+                             (1- (point)) 'invisible))
+                 (forward-line -1)
+                 (magit-section-goto (magit-current-section))))))))))
+
+(defun magit-section-up ()
+  "Move to the beginning of the parent section."
+  (interactive)
+  (--if-let (oref (magit-current-section) parent)
+      (magit-section-goto it)
+    (user-error "No parent section")))
+
+(defun magit-section-forward-sibling ()
+  "Move to the beginning of the next sibling section.
+If there is no next sibling section, then move to the parent."
+  (interactive)
+  (let ((current (magit-current-section)))
+    (if (oref current parent)
+        (--if-let (car (magit-section-siblings current 'next))
+            (magit-section-goto it)
+          (magit-section-forward))
+      (magit-section-goto 1))))
+
+(defun magit-section-backward-sibling ()
+  "Move to the beginning of the previous sibling section.
+If there is no previous sibling section, then move to the parent."
+  (interactive)
+  (let ((current (magit-current-section)))
+    (if (oref current parent)
+        (--if-let (car (magit-section-siblings current 'prev))
+            (magit-section-goto it)
+          (magit-section-backward))
+      (magit-section-goto -1))))
+
+(defun magit-section-goto (arg)
+  (if (integerp arg)
+      (progn (forward-line arg)
+             (setq arg (magit-current-section)))
+    (goto-char (oref arg start)))
+  (run-hook-with-args 'magit-section-movement-hook arg))
+
+(defun magit-section-set-window-start (section)
+  "Ensure the beginning of SECTION is visible."
+  (unless (pos-visible-in-window-p (oref section end))
+    (set-window-start (selected-window) (oref section start))))
+
+(defun magit-hunk-set-window-start (section)
+  "When SECTION is a `hunk', ensure that its beginning is visible.
+It the SECTION has a different type, then do nothing."
+  (when (magit-hunk-section-p section)
+    (magit-section-set-window-start section)))
+
+(defmacro magit-define-section-jumper (name heading type &optional value)
+  "Define an interactive function to go some section.
+Together TYPE and VALUE identify the section.
+HEADING is the displayed heading of the section."
+  (declare (indent defun))
+  `(defun ,name (&optional expand) ,(format "\
+Jump to the section \"%s\".
+With a prefix argument also expand it." heading)
+     (interactive "P")
+     (--if-let (magit-get-section
+                (cons (cons ',type ,value)
+                      (magit-section-ident magit-root-section)))
+         (progn (goto-char (oref it start))
+                (when expand
+                  (with-local-quit (magit-section-show it))
+                  (recenter 0)))
+       (message ,(format "Section \"%s\" wasn't found" heading)))))
+
+;;;; Visibility
+
+(defun magit-section-show (section)
+  "Show the body of the current section."
+  (interactive (list (magit-current-section)))
+  (oset section hidden nil)
+  (when-let ((washer (oref section washer)))
+    (oset section washer nil)
+    (let ((inhibit-read-only t)
+          (magit-insert-section--parent section)
+          (content (oref section content)))
+      (save-excursion
+        (if (and content (< content (oref section end)))
+            (funcall washer section) ; already partially washed (hunk)
+          (goto-char (oref section end))
+          (oset section content (point-marker))
+          (funcall washer)
+          (oset section end (point-marker)))))
+    (magit-section-update-highlight))
+  (when-let ((beg (oref section content)))
+    (remove-overlays beg (oref section end) 'invisible t))
+  (magit-section-maybe-cache-visibility section)
+  (dolist (child (oref section children))
+    (if (oref child hidden)
+        (magit-section-hide child)
+      (magit-section-show child))))
+
+(defun magit-section-hide (section)
+  "Hide the body of the current section."
+  (interactive (list (magit-current-section)))
+  (if (eq section magit-root-section)
+      (user-error "Cannot hide root section")
+    (oset section hidden t)
+    (when-let ((beg (oref section content)))
+      (let ((end (oref section end)))
+        (remove-overlays beg end 'invisible t)
+        (let ((o (make-overlay beg end)))
+          (overlay-put o 'evaporate t)
+          (overlay-put o 'invisible t))))
+    (magit-section-maybe-cache-visibility section)))
+
+(defun magit-section-toggle (section)
+  "Toggle visibility of the body of the current section."
+  (interactive (list (magit-current-section)))
+  (if (eq section magit-root-section)
+      (user-error "Cannot hide root section")
+    (goto-char (oref section start))
+    (if (oref section hidden)
+        (magit-section-show section)
+      (magit-section-hide section))))
+
+(defun magit-section-toggle-children (section)
+  "Toggle visibility of bodies of children of the current section."
+  (interactive (list (magit-current-section)))
+  (goto-char (oref section start))
+  (let* ((children (oref section children))
+         (show (--any-p (oref it hidden) children)))
+    (dolist (c children)
+      (oset c hidden show)))
+  (magit-section-show section))
+
+(defun magit-section-show-children (section &optional depth)
+  "Recursively show the bodies of children of the current section.
+With a prefix argument show children that deep and hide deeper
+children."
+  (interactive (list (magit-current-section)))
+  (magit-section-show-children-1 section depth)
+  (magit-section-show section))
+
+(defun magit-section-show-children-1 (section &optional depth)
+  (dolist (child (oref section children))
+    (oset child hidden nil)
+    (if depth
+        (if (> depth 0)
+            (magit-section-show-children-1 child (1- depth))
+          (magit-section-hide child))
+      (magit-section-show-children-1 child))))
+
+(defun magit-section-hide-children (section)
+  "Recursively hide the bodies of children of the current section."
+  (interactive (list (magit-current-section)))
+  (mapc 'magit-section-hide (oref section children)))
+
+(defun magit-section-show-headings (section)
+  "Recursively show headings of children of the current section.
+Only show the headings, previously shown text-only bodies are
+hidden."
+  (interactive (list (magit-current-section)))
+  (magit-section-show-headings-1 section)
+  (magit-section-show section))
+
+(defun magit-section-show-headings-1 (section)
+  (dolist (child (oref section children))
+    (oset child hidden nil)
+    (when (or (oref child children)
+              (not (oref child content)))
+      (magit-section-show-headings-1 child))))
+
+(defun magit-section-cycle (section)
+  "Cycle visibility of current section and its children."
+  (interactive (list (magit-current-section)))
+  (goto-char (oref section start))
+  (if (oref section hidden)
+      (progn (magit-section-show section)
+             (magit-section-hide-children section))
+    (let ((children (oref section children)))
+      (cond ((and (--any-p (oref it hidden)   children)
+                  (--any-p (oref it children) children))
+             (magit-section-show-headings section))
+            ((-any-p 'magit-section-hidden-body children)
+             (magit-section-show-children section))
+            (t
+             (magit-section-hide section))))))
+
+(defun magit-section-cycle-global ()
+  "Cycle visibility of all sections in the current buffer."
+  (interactive)
+  (let ((children (oref magit-root-section children)))
+    (cond ((and (--any-p (oref it hidden)   children)
+                (--any-p (oref it children) children))
+           (magit-section-show-headings magit-root-section))
+          ((-any-p 'magit-section-hidden-body children)
+           (magit-section-show-children magit-root-section))
+          (t
+           (mapc 'magit-section-hide children)))))
+
+(defun magit-section-cycle-diffs ()
+  "Cycle visibility of diff-related sections in the current buffer."
+  (interactive)
+  (when-let ((sections
+              (cond ((derived-mode-p 'magit-status-mode)
+                     (--mapcat
+                      (when it
+                        (when (oref it hidden)
+                          (magit-section-show it))
+                        (oref it children))
+                      (list (magit-get-section '((staged)   (status)))
+                            (magit-get-section '((unstaged) (status))))))
+                    ((derived-mode-p 'magit-diff-mode)
+                     (-filter #'magit-file-section-p
+                              (oref magit-root-section children))))))
+    (if (--any-p (oref it hidden) sections)
+        (dolist (s sections)
+          (magit-section-show s)
+          (magit-section-hide-children s))
+      (let ((children (--mapcat (oref it children) sections)))
+        (cond ((and (--any-p (oref it hidden)   children)
+                    (--any-p (oref it children) children))
+               (mapc 'magit-section-show-headings sections))
+              ((-any-p 'magit-section-hidden-body children)
+               (mapc 'magit-section-show-children sections))
+              (t
+               (mapc 'magit-section-hide sections)))))))
+
+(defun magit-section-hidden-body (section &optional pred)
+  (--if-let (oref section children)
+      (funcall (or pred '-any-p) 'magit-section-hidden-body it)
+    (and (oref section content)
+         (oref section hidden))))
+
+(defun magit-section-invisible-p (section)
+  "Return t if the SECTION's body is invisible.
+When the body of an ancestor of SECTION is collapsed then
+SECTION's body (and heading) obviously cannot be visible."
+  (or (oref section hidden)
+      (--when-let (oref section parent)
+        (magit-section-invisible-p it))))
+
+(defun magit-section-show-level (level)
+  "Show surrounding sections up to LEVEL.
+If LEVEL is negative, show up to the absolute value.
+Sections at higher levels are hidden."
+  (if (< level 0)
+      (let ((s (magit-current-section)))
+        (setq level (- level))
+        (while (> (1- (length (magit-section-ident s))) level)
+          (setq s (oref s parent))
+          (goto-char (oref s start)))
+        (magit-section-show-children magit-root-section (1- level)))
+    (cl-do* ((s (magit-current-section)
+                (oref s parent))
+             (i (1- (length (magit-section-ident s)))
+                (cl-decf i)))
+        ((cond ((< i level) (magit-section-show-children s (- level i 1)) t)
+               ((= i level) (magit-section-hide s) t))
+         (magit-section-goto s)))))
+
+(defun magit-section-show-level-1 ()
+  "Show surrounding sections on first level."
+  (interactive)
+  (magit-section-show-level 1))
+
+(defun magit-section-show-level-1-all ()
+  "Show all sections on first level."
+  (interactive)
+  (magit-section-show-level -1))
+
+(defun magit-section-show-level-2 ()
+  "Show surrounding sections up to second level."
+  (interactive)
+  (magit-section-show-level 2))
+
+(defun magit-section-show-level-2-all ()
+  "Show all sections up to second level."
+  (interactive)
+  (magit-section-show-level -2))
+
+(defun magit-section-show-level-3 ()
+  "Show surrounding sections up to third level."
+  (interactive)
+  (magit-section-show-level 3))
+
+(defun magit-section-show-level-3-all ()
+  "Show all sections up to third level."
+  (interactive)
+  (magit-section-show-level -3))
+
+(defun magit-section-show-level-4 ()
+  "Show surrounding sections up to fourth level."
+  (interactive)
+  (magit-section-show-level 4))
+
+(defun magit-section-show-level-4-all ()
+  "Show all sections up to fourth level."
+  (interactive)
+  (magit-section-show-level -4))
+
+;;;; Auxiliary
+
+(defun magit-describe-section ()
+  "Show information about the section at point.
+This command is intended for debugging purposes."
+  (interactive)
+  (let ((section (magit-current-section)))
+    (message "%S %S %s-%s"
+             (oref section value)
+             (magit-section-lineage section)
+             (marker-position (oref section start))
+             (marker-position (oref section end)))))
+
+;;; Match
+
+(cl-defun magit-section-match
+    (condition &optional (section (magit-current-section)))
+  "Return t if SECTION matches CONDITION.
+
+SECTION defaults to the section at point.  If SECTION is not
+specified and there also is no section at point, then return
+nil.
+
+CONDITION can take the following forms:
+  (CONDITION...)  matches if any of the CONDITIONs matches.
+  [TYPE...]       matches if the first TYPE matches the type
+                  of the section, the second matches that of
+                  its parent, and so on.
+  [* TYPE...]     matches sections that match [TYPE...] and
+                  also recursively all their child sections.
+  TYPE            matches sections of TYPE regardless of the
+                  types of the parent sections.
+
+Each TYPE is a symbol.  Note that it is not necessary to specify
+all TYPEs up to the root section as printed by
+`magit-describe-type', unless of course you want to be that
+precise."
+  (and section
+       (magit-section-match-1 condition
+                              (mapcar #'car (magit-section-ident section)))))
+
+(defun magit-section-match-1 (condition type-list)
+  (if (listp condition)
+      (--first (magit-section-match-1 it type-list) condition)
+    (magit-section-match-2 (if (symbolp condition)
+                               (list condition)
+                             (append condition nil))
+                           type-list)))
+
+(defun magit-section-match-2 (l1 l2)
+  (or (null l1)
+      (if (eq (car l1) '*)
+          (or (magit-section-match-2 (cdr l1) l2)
+              (and l2
+                   (magit-section-match-2 l1 (cdr l2))))
+        (and l2
+             (equal (car l1) (car l2))
+             (magit-section-match-2 (cdr l1) (cdr l2))))))
+
+(defmacro magit-section-when (condition &rest body)
+  "If the section at point matches CONDITION, evaluate BODY.
+
+If the section matches, then evaluate BODY forms sequentially
+with `it' bound to the section and return the value of the last
+form.  If there are no BODY forms, then return the value of the
+section.  If the section does not match or if there is no section
+at point, then return nil.
+
+See `magit-section-match' for the forms CONDITION can take."
+  (declare (indent 1)
+           (debug (sexp body)))
+  `(--when-let (magit-current-section)
+     ;; Quoting CONDITION here often leads to double-quotes, which
+     ;; isn't an issue because `magit-section-match-1' implicitly
+     ;; deals with that.  We shouldn't force users of this function
+     ;; to not quote CONDITION because that would needlessly break
+     ;; backward compatibility.
+     (when (magit-section-match ',condition it)
+       ,@(or body '((oref it value))))))
+
+(defmacro magit-section-case (&rest clauses)
+  "Choose among clauses on the type of the section at point.
+
+Each clause looks like (CONDITION BODY...).  The type of the
+section is compared against each CONDITION; the BODY forms of the
+first match are evaluated sequentially and the value of the last
+form is returned.  Inside BODY the symbol `it' is bound to the
+section at point.  If no clause succeeds or if there is no
+section at point, return nil.
+
+See `magit-section-match' for the forms CONDITION can take.
+Additionally a CONDITION of t is allowed in the final clause, and
+matches if no other CONDITION match, even if there is no section
+at point."
+  (declare (indent 0)
+           (debug (&rest (sexp body))))
+  (let ((lineage (cl-gensym "lineage")))
+    `(let* ((it (magit-current-section))
+            (,lineage (and it (append (magit-section-lineage it) nil))))
+       (cond ,@(mapcar (lambda (clause)
+                         `(,(or (eq (car clause) t)
+                                `(and it (magit-section-match-1
+                                          ',(car clause) ,lineage)))
+                           ,@(cdr clause)))
+                       clauses)))))
+
+(defun magit-section-match-assoc (section alist)
+  "Return the value associated with SECTION's type or lineage in ALIST."
+  (let ((ident (mapcar #'car (magit-section-ident section))))
+    (-some (pcase-lambda (`(,key . ,val))
+             (and (magit-section-match-1 key ident) val))
+           alist)))
+
+;;; Create
+
+(defvar magit-insert-section-hook nil
+  "Hook run after `magit-insert-section's BODY.
+Avoid using this hook and only ever do so if you know
+what you are doing and are sure there is no other way.")
+
+(defmacro magit-insert-section (&rest args)
+  "Insert a section at point.
+
+TYPE is the section type, a symbol.  Many commands that act on
+the current section behave differently depending on that type.
+Also if a variable `magit-TYPE-section-map' exists, then use
+that as the text-property `keymap' of all text belonging to the
+section (but this may be overwritten in subsections).  TYPE can
+also have the form `(eval FORM)' in which case FORM is evaluated
+at runtime.
+
+Optional VALUE is the value of the section, usually a string
+that is required when acting on the section.
+
+When optional HIDE is non-nil collapse the section body by
+default, i.e. when first creating the section, but not when
+refreshing the buffer.  Else expand it by default.  This can be
+overwritten using `magit-section-set-visibility-hook'.  When a
+section is recreated during a refresh, then the visibility of
+predecessor is inherited and HIDE is ignored (but the hook is
+still honored).
+
+BODY is any number of forms that actually insert the section's
+heading and body.  Optional NAME, if specified, has to be a
+symbol, which is then bound to the struct of the section being
+inserted.
+
+Before BODY is evaluated the `start' of the section object is set
+to the value of `point' and after BODY was evaluated its `end' is
+set to the new value of `point'; BODY is responsible for moving
+`point' forward.
+
+If it turns out inside BODY that the section is empty, then
+`magit-cancel-section' can be used to abort and remove all traces
+of the partially inserted section.  This can happen when creating
+a section by washing Git's output and Git didn't actually output
+anything this time around.
+
+\(fn [NAME] (TYPE &optional VALUE HIDE) &rest BODY)"
+  (declare (indent defun)
+           (debug ([&optional symbolp]
+                   (&or [("eval" symbolp) &optional form form]
+                        [symbolp &optional form form])
+                   body)))
+  (let ((tp (cl-gensym "type"))
+        (s* (and (symbolp (car args))
+                 (pop args)))
+        (s  (cl-gensym "section")))
+    `(let* ((,tp ,(let ((type (nth 0 (car args))))
+                    (if (eq (car-safe type) 'eval)
+                        (cadr type)
+                      `',type)))
+            (,s (funcall (pcase ,tp
+                           (`file 'magit-file-section)
+                           (`hunk 'magit-hunk-section)
+                           (_     'magit-section))
+                         :type ,tp
+                         :value ,(nth 1 (car args))
+                         :start (point-marker)
+                         :parent magit-insert-section--parent)))
+       (oset ,s hidden
+             (if-let ((value (run-hook-with-args-until-success
+                              'magit-section-set-visibility-hook ,s)))
+                 (eq value 'hide)
+               (if-let ((incarnation (and magit-insert-section--oldroot
+                                          (magit-get-section
+                                           (magit-section-ident ,s)
+                                           magit-insert-section--oldroot))))
+                   (oref incarnation hidden)
+                 (if-let ((value (magit-section-match-assoc
+                                  ,s magit-section-initial-visibility-alist)))
+                     (progn
+                       (when (functionp value)
+                         (setq value (funcall value ,s)))
+                       (eq value 'hide))
+                   ,(nth 2 (car args))))))
+       (let ((magit-insert-section--current ,s)
+             (magit-insert-section--parent  ,s)
+             (magit-insert-section--oldroot
+              (or magit-insert-section--oldroot
+                  (unless magit-insert-section--parent
+                    (prog1 magit-root-section
+                      (setq magit-root-section ,s))))))
+         (catch 'cancel-section
+           ,@(if s*
+                 `((let ((,s* ,s))
+                     ,@(cdr args)))
+               (cdr args))
+           (run-hooks 'magit-insert-section-hook)
+           (magit-insert-child-count ,s)
+           (set-marker-insertion-type (oref ,s start) t)
+           (let* ((end (oset ,s end (point-marker)))
+                  (map (intern (format "magit-%s-section-map" (oref ,s type))))
+                  (map (and (boundp map) (symbol-value map))))
+             (save-excursion
+               (goto-char (oref ,s start))
+               (while (< (point) end)
+                 (let ((next (or (next-single-property-change
+                                  (point) 'magit-section)
+                                 end)))
+                   (unless (get-text-property (point) 'magit-section)
+                     (put-text-property (point) next 'magit-section ,s)
+                     (when map
+                       (put-text-property (point) next 'keymap map)))
+                   (goto-char next)))))
+           (if (eq ,s magit-root-section)
+               (let ((magit-section-cache-visibility nil))
+                 (magit-section-show ,s))
+             (oset (oref ,s parent) children
+                   (nconc (oref (oref ,s parent) children)
+                          (list ,s)))))
+         ,s))))
+
+(defun magit-cancel-section ()
+  (when magit-insert-section--current
+    (if (not (oref magit-insert-section--current parent))
+        (insert "(empty)\n")
+      (delete-region (oref magit-insert-section--current start)
+                     (point))
+      (setq magit-insert-section--current nil)
+      (throw 'cancel-section nil))))
+
+(defun magit-insert-heading (&rest args)
+  "Insert the heading for the section currently being inserted.
+
+This function should only be used inside `magit-insert-section'.
+
+When called without any arguments, then just set the `content'
+slot of the object representing the section being inserted to
+a marker at `point'.  The section should only contain a single
+line when this function is used like this.
+
+When called with arguments ARGS, which have to be strings, or
+nil, then insert those strings at point.  The section should not
+contain any text before this happens and afterwards it should
+again only contain a single line.  If the `face' property is set
+anywhere inside any of these strings, then insert all of them
+unchanged.  Otherwise use the `magit-section-heading' face for
+all inserted text.
+
+The `content' property of the section struct is the end of the
+heading (which lasts from `start' to `content') and the beginning
+of the the body (which lasts from `content' to `end').  If the
+value of `content' is nil, then the section has no heading and
+its body cannot be collapsed.  If a section does have a heading,
+then its height must be exactly one line, including a trailing
+newline character.  This isn't enforced, you are responsible for
+getting it right.  The only exception is that this function does
+insert a newline character if necessary."
+  (declare (indent defun))
+  (when args
+    (let ((heading (apply #'concat args)))
+      (insert (if (text-property-not-all 0 (length heading) 'face nil heading)
+                  heading
+                (propertize heading 'face 'magit-section-heading)))))
+  (unless (bolp)
+    (insert ?\n))
+  (magit-maybe-make-margin-overlay)
+  (oset magit-insert-section--current content (point-marker)))
+
+(defvar magit-insert-headers--hook nil "For internal use only.")
+(defvar magit-insert-headers--beginning nil "For internal use only.")
+
+(defun magit-insert-headers (hooks)
+  (let ((magit-insert-section-hook
+         (cons 'magit-insert-remaining-headers
+               (if (listp magit-insert-section-hook)
+                   magit-insert-section-hook
+                 (list magit-insert-section-hook))))
+        (magit-insert-headers--hook hooks)
+        wrapper)
+    (setq magit-insert-headers--beginning (point))
+    (while (and (setq wrapper (pop magit-insert-headers--hook))
+                (= (point) magit-insert-headers--beginning))
+      (funcall wrapper))))
+
+(defun magit-insert-remaining-headers ()
+  (if (= (point) magit-insert-headers--beginning)
+      (magit-cancel-section)
+    (magit-insert-heading)
+    (remove-hook 'magit-insert-section-hook 'magit-insert-remaining-headers)
+    (mapc #'funcall magit-insert-headers--hook)
+    (insert "\n")))
+
+(defun magit-insert-child-count (section)
+  "Modify SECTION's heading to contain number of child sections.
+
+If `magit-section-show-child-count' is non-nil and the SECTION
+has children and its heading ends with \":\", then replace that
+with \" (N)\", where N is the number of child sections.
+
+This function is called by `magit-insert-section' after that has
+evaluated its BODY.  Admittedly that's a bit of a hack."
+  ;; This has to be fast, not pretty!
+  (let (content count)
+    (when (and magit-section-show-child-count
+               (setq count (length (oref section children)))
+               (> count 0)
+               (setq content (oref section content))
+               (eq (char-before (1- content)) ?:))
+      (save-excursion
+        (goto-char (- content 2))
+        (insert (format " (%s)" count))
+        (delete-char 1)))))
+
+;;; Update
+
+(defvar-local magit-section-highlight-overlays nil)
+(defvar-local magit-section-highlighted-section nil)
+(defvar-local magit-section-highlighted-sections nil)
+(defvar-local magit-section-unhighlight-sections nil)
+
+(defun magit-section-update-region (_)
+  "When the region is a valid section-selection, highlight them all."
+  ;; At least that's what it does conceptually.  In actuality it just
+  ;; returns a list of those sections, and it doesn't even matter if
+  ;; this is a member of `magit-region-highlight-hook'.  It probably
+  ;; should be removed, but I want to make sure before removing it.
+  (magit-region-sections))
+
+(defun magit-section-update-highlight ()
+  (let ((section (magit-current-section)))
+    (unless (eq section magit-section-highlighted-section)
+      (let ((inhibit-read-only t)
+            (deactivate-mark nil)
+            (selection (magit-region-sections)))
+        (mapc #'delete-overlay magit-section-highlight-overlays)
+        (setq magit-section-highlight-overlays nil)
+        (setq magit-section-unhighlight-sections
+              magit-section-highlighted-sections)
+        (setq magit-section-highlighted-sections nil)
+        (unless (eq section magit-root-section)
+          (run-hook-with-args-until-success
+           'magit-section-highlight-hook section selection))
+        (dolist (s magit-section-unhighlight-sections)
+          (run-hook-with-args-until-success
+           'magit-section-unhighlight-hook s selection))
+        (restore-buffer-modified-p nil)
+        (unless (eq magit-section-highlighted-section section)
+          (setq magit-section-highlighted-section
+                (and (not (oref section hidden))
+                     section))))
+      (when (version< emacs-version "25.1")
+        (setq deactivate-mark nil)))))
+
+(defun magit-section-highlight (section selection)
+  "Highlight SECTION and if non-nil all sections in SELECTION.
+This function works for any section but produces undesirable
+effects for diff related sections, which by default are
+highlighted using `magit-diff-highlight'.  Return t."
+  (cond (selection
+         (magit-section-make-overlay (oref (car selection) start)
+                                     (oref (car (last selection)) end)
+                                     'magit-section-highlight)
+         (magit-section-highlight-selection nil selection))
+        (t
+         (magit-section-make-overlay (oref section start)
+                                     (oref section end)
+                                     'magit-section-highlight)))
+  t)
+
+(defun magit-section-highlight-selection (_ selection)
+  "Highlight the section-selection region.
+If SELECTION is non-nil, then it is a list of sections selected by
+the region.  The headings of these sections are then highlighted.
+
+This is a fallback for people who don't want to highlight the
+current section and therefore removed `magit-section-highlight'
+from `magit-section-highlight-hook'.
+
+This function is necessary to ensure that a representation of
+such a region is visible.  If neither of these functions were
+part of the hook variable, then such a region would be
+invisible."
+  (when (and selection
+             (not (and (eq this-command 'mouse-drag-region))))
+    (dolist (section selection)
+      (magit-section-make-overlay (oref section start)
+                                  (or (oref section content)
+                                      (oref section end))
+                                  'magit-section-heading-selection))
+    t))
+
+(defun magit-section-make-overlay (start end face)
+  ;; Yes, this doesn't belong here.  But the alternative of
+  ;; spreading this hack across the code base is even worse.
+  (when (and magit-keep-region-overlay
+             (memq face '(magit-section-heading-selection
+                          magit-diff-file-heading-selection
+                          magit-diff-hunk-heading-selection)))
+    (setq face (list :foreground (face-foreground face))))
+  (let ((ov (make-overlay start end nil t)))
+    (overlay-put ov 'face face)
+    (overlay-put ov 'evaporate t)
+    (push ov magit-section-highlight-overlays)
+    ov))
+
+(defun magit-section-goto-successor (section line char arg)
+  (let ((ident (magit-section-ident section)))
+    (--if-let (magit-get-section ident)
+        (let ((start (oref it start)))
+          (goto-char start)
+          (unless (eq it magit-root-section)
+            (ignore-errors
+              (forward-line line)
+              (forward-char char))
+            (unless (eq (magit-current-section) it)
+              (goto-char start))))
+      (or (and (magit-hunk-section-p section)
+               (when-let ((parent (magit-get-section
+                                   (magit-section-ident
+                                    (oref section parent)))))
+                 (let* ((children (oref parent children))
+                        (siblings (magit-section-siblings section 'prev))
+                        (previous (nth (length siblings) children)))
+                   (if (not arg)
+                       (--when-let (or previous (car (last children)))
+                         (magit-section-goto it)
+                         t)
+                     (when previous
+                       (magit-section-goto previous))
+                     (if (and (stringp arg)
+                              (re-search-forward arg (oref parent end) t))
+                         (goto-char (match-beginning 0))
+                       (goto-char (oref (car (last children)) end))
+                       (forward-line -1)
+                       (while (looking-at "^ ")    (forward-line -1))
+                       (while (looking-at "^[-+]") (forward-line -1))
+                       (forward-line))))))
+          (goto-char (--if-let (magit-section-goto-successor-1 section)
+                         (if (eq (oref it type) 'button)
+                             (point-min)
+                           (oref it start))
+                       (point-min)))))))
+
+(defun magit-section-goto-successor-1 (section)
+  (or (--when-let (pcase (oref section type)
+                    (`staged 'unstaged)
+                    (`unstaged 'staged)
+                    (`unpushed 'unpulled)
+                    (`unpulled 'unpushed))
+        (magit-get-section `((,it) (status))))
+      (--when-let (car (magit-section-siblings section 'next))
+        (magit-get-section (magit-section-ident it)))
+      (--when-let (car (magit-section-siblings section 'prev))
+        (magit-get-section (magit-section-ident it)))
+      (--when-let (oref section parent)
+        (or (magit-get-section (magit-section-ident it))
+            (magit-section-goto-successor-1 it)))))
+
+;;; Visibility
+
+(defvar-local magit-section-visibility-cache nil)
+(put 'magit-section-visibility-cache 'permanent-local t)
+
+(defun magit-section-cached-visibility (section)
+  "Set SECTION's visibility to the cached value."
+  (cdr (assoc (magit-section-ident section)
+              magit-section-visibility-cache)))
+
+(cl-defun magit-section-cache-visibility
+    (&optional (section magit-insert-section--current))
+  ;; Emacs 25's `alist-get' lacks TESTFN.
+  (let* ((id  (magit-section-ident section))
+         (elt (assoc id magit-section-visibility-cache))
+         (val (if (oref section hidden) 'hide 'show)))
+    (if elt
+        (setcdr elt val)
+      (push (cons id val) magit-section-visibility-cache))))
+
+(cl-defun magit-section-maybe-cache-visibility
+    (&optional (section magit-insert-section--current))
+  (when (or (eq magit-section-cache-visibility t)
+            (memq (oref section type)
+                  magit-section-cache-visibility))
+    (magit-section-cache-visibility section)))
+
+(defun magit-preserve-section-visibility-cache ()
+  (when (derived-mode-p 'magit-status-mode 'magit-refs-mode)
+    (magit-repository-local-set
+     (cons major-mode 'magit-section-visibility-cache)
+     magit-section-visibility-cache)))
+
+(defun magit-restore-section-visibility-cache (mode)
+  (setq magit-section-visibility-cache
+        (magit-repository-local-get
+         (cons mode 'magit-section-visibility-cache))))
+
+;;; Utilities
+
+(cl-defun magit-section-selected-p (section &optional (selection nil sselection))
+  (and (not (eq section magit-root-section))
+       (or  (eq section (magit-current-section))
+            (memq section (if sselection
+                              selection
+                            (setq selection (magit-region-sections))))
+            (--when-let (oref section parent)
+              (magit-section-selected-p it selection)))))
+
+(defun magit-section-parent-value (section)
+  (when-let ((parent (oref section parent)))
+    (oref parent value)))
+
+(defun magit-section-siblings (section &optional direction)
+  "Return a list of the sibling sections of SECTION.
+
+If optional DIRECTION is `prev', then return siblings that come
+before SECTION.  If it is `next', then return siblings that come
+after SECTION.  For all other values, return all siblings
+excluding SECTION itself."
+  (when-let ((parent (oref section parent)))
+    (let ((siblings (oref parent children)))
+      (pcase direction
+        (`prev  (cdr (member section (reverse siblings))))
+        (`next  (cdr (member section siblings)))
+        (_      (remq section siblings))))))
+
+(defun magit-region-values (&optional types multiple)
+  "Return a list of the values of the selected sections.
+
+Also see `magit-region-sections' whose doc-string explains when a
+region is a valid section selection.  If the region is not active
+or is not a valid section selection, then return nil.  If optional
+TYPES is non-nil then the selection not only has to be valid; the
+types of all selected sections additionally have to match one of
+TYPES, or nil is returned."
+  (--map (oref it value)
+         (magit-region-sections types multiple)))
+
+(defun magit-region-sections (&optional types multiple)
+  "Return a list of the selected sections.
+
+When the region is active and constitutes a valid section
+selection, then return a list of all selected sections.  This is
+the case when the region begins in the heading of a section and
+ends in the heading of the same section or in that of a sibling
+section.  If optional MULTIPLE is non-nil, then the region cannot
+begin and end in the same section.
+
+When the selection is not valid, then return nil.  In this case,
+most commands that can act on the selected sections will instead
+act on the section at point.
+
+When the region looks like it would in any other buffer then
+the selection is invalid.  When the selection is valid then the
+region uses the `magit-section-highlight' face.  This does not
+apply to diffs where things get a bit more complicated, but even
+here if the region looks like it usually does, then that's not
+a valid selection as far as this function is concerned.
+
+If optional TYPES is non-nil, then the selection not only has to
+be valid; the types of all selected sections additionally have
+to match one of TYPES, or nil is returned.  TYPES can also be a
+single type, instead of a list of types."
+  (when (region-active-p)
+    (let* ((rbeg (region-beginning))
+           (rend (region-end))
+           (sbeg (get-text-property rbeg 'magit-section))
+           (send (get-text-property rend 'magit-section)))
+      (when (and send
+                 (not (eq send magit-root-section))
+                 (not (and multiple (eq send sbeg))))
+        (let ((siblings (cons sbeg (magit-section-siblings sbeg 'next)))
+              sections)
+          (when (and (memq send siblings)
+                     (magit-section-position-in-heading-p sbeg rbeg)
+                     (magit-section-position-in-heading-p send rend))
+            (while siblings
+              (push (car siblings) sections)
+              (when (eq (pop siblings) send)
+                (setq siblings nil)))
+            (setq sections (nreverse sections))
+            (when (and types (symbolp types))
+              (setq types (list types)))
+            (when (or (not types)
+                      (--all-p (memq (oref it type) types) sections))
+              sections)))))))
+
+(defun magit-section-position-in-heading-p (&optional section pos)
+  "Return t if POSITION is inside the heading of SECTION.
+POSITION defaults to point and SECTION defaults to the
+current section."
+  (unless section
+    (setq section (magit-current-section)))
+  (unless pos
+    (setq pos (point)))
+  (and section
+       (>= pos (oref section start))
+       (<  pos (or (oref section content)
+                   (oref section end)))
+       t))
+
+(defun magit-section-internal-region-p (&optional section)
+  "Return t if the region is active and inside SECTION's body.
+If optional SECTION is nil, use the current section."
+  (and (region-active-p)
+       (or section (setq section (magit-current-section)))
+       (let ((beg (get-text-property (region-beginning) 'magit-section)))
+         (and (eq beg (get-text-property   (region-end) 'magit-section))
+              (eq beg section)))
+       (not (or (magit-section-position-in-heading-p section (region-beginning))
+                (magit-section-position-in-heading-p section (region-end))))
+       t))
+
+(defun magit-section--backward-protected ()
+  "Move to the beginning of the current or the previous visible section.
+Same as `magit-section-backward' but for non-interactive use.
+Suppress `magit-section-movement-hook', and return a boolean to
+indicate whether a section was found, instead of raising an error
+if not."
+  (condition-case nil
+      (let ((magit-section-movement-hook nil))
+        (magit-section-backward)
+        t)
+    (user-error nil)))
+
+(defun magit-section--backward-find (predicate)
+  "Move to the first previous section satisfying PREDICATE.
+PREDICATE does not take any parameter and should not move
+point."
+  (let (found)
+    (while (and (setq found (magit-section--backward-protected))
+                (not (funcall predicate))))
+    found))
+
+(defun magit-wash-sequence (function)
+  "Repeatedly call FUNCTION until it returns nil or eob is reached.
+FUNCTION has to move point forward or return nil."
+  (while (and (not (eobp)) (funcall function))))
+
+(defun magit-add-section-hook (hook function &optional at append local)
+  "Add to the value of section hook HOOK the function FUNCTION.
+
+Add FUNCTION at the beginning of the hook list unless optional
+APPEND is non-nil, in which case FUNCTION is added at the end.
+If FUNCTION already is a member, then move it to the new location.
+
+If optional AT is non-nil and a member of the hook list, then
+add FUNCTION next to that instead.  Add before or after AT, or
+replace AT with FUNCTION depending on APPEND.  If APPEND is the
+symbol `replace', then replace AT with FUNCTION.  For any other
+non-nil value place FUNCTION right after AT.  If nil, then place
+FUNCTION right before AT.  If FUNCTION already is a member of the
+list but AT is not, then leave FUNCTION where ever it already is.
+
+If optional LOCAL is non-nil, then modify the hook's buffer-local
+value rather than its global value.  This makes the hook local by
+copying the default value.  That copy is then modified.
+
+HOOK should be a symbol.  If HOOK is void, it is first set to nil.
+HOOK's value must not be a single hook function.  FUNCTION should
+be a function that takes no arguments and inserts one or multiple
+sections at point, moving point forward.  FUNCTION may choose not
+to insert its section(s), when doing so would not make sense.  It
+should not be abused for other side-effects.  To remove FUNCTION
+again use `remove-hook'."
+  (unless (boundp hook)
+    (error "Cannot add function to undefined hook variable %s" hook))
+  (or (default-boundp hook) (set-default hook nil))
+  (let ((value (if local
+                   (if (local-variable-p hook)
+                       (symbol-value hook)
+                     (unless (local-variable-if-set-p hook)
+                       (make-local-variable hook))
+                     (copy-sequence (default-value hook)))
+                 (default-value hook))))
+    (if at
+        (when (setq at (member at value))
+          (setq value (delq function value))
+          (cond ((eq append 'replace)
+                 (setcar at function))
+                (append
+                 (push function (cdr at)))
+                (t
+                 (push (car at) (cdr at))
+                 (setcar at function))))
+      (setq value (delq function value)))
+    (unless (member function value)
+      (setq value (if append
+                      (append value (list function))
+                    (cons function value))))
+    (when (eq append 'replace)
+      (setq value (delq at value)))
+    (if local
+        (set hook value)
+      (set-default hook value))))
+
+(defun magit-run-section-hook (hook)
+  "Run HOOK, warning about invalid entries."
+  (--if-let (-remove #'functionp (symbol-value hook))
+      (progn
+        (message "`%s' contains entries that are no longer valid.
+%s\nUsing standard value instead.  Please re-configure hook variable."
+                 hook
+                 (mapconcat (lambda (sym) (format "  `%s'" sym)) it "\n"))
+        (sit-for 5)
+        (defvar magit--hook-standard-value nil)
+        (let ((magit--hook-standard-value
+               (eval (car (get hook 'standard-value)))))
+          (run-hooks 'magit---hook-standard-value)))
+    (run-hooks hook)))
+
+(provide 'magit-section)
+;;; magit-section.el ends here