[elpa] externals/org 555dacfa8b: org-persist: Merge index with index file content

[ELPA Syncer]

branch: externals/org
commit 555dacfa8bec7b326a728abc2a9905501e05195a
Author: TEC <git@tecosaur.net>
Commit: TEC <git@tecosaur.net>

    org-persist: Merge index with index file content
    
    * lisp/org-persist.el (org-persist-write, org-persist-load,
    org-persist-write:index, org-persist-load:index): Check if the index
    file has been externally updated since loading, and if so try to perform
    basic merging of the current index file contents and the loaded index
    before performing GC or overwriting the index file.
    (org-persist--index-age, org-persist--merge-index-with-disk,
    org-persist--merge-index): New variable and functions to keep track of
    index age and perform merging.
---
 lisp/org-persist.el | 56 ++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 49 insertions(+), 7 deletions(-)

diff --git a/lisp/org-persist.el b/lisp/org-persist.el
index aff99f8136..dfc62d0e37 100644
--- a/lisp/org-persist.el
+++ b/lisp/org-persist.el
@@ -259,6 +259,9 @@ properties:
   "Hash table storing `org-persist--index'.  Used for quick access.
 They keys are conses of (container . associated).")
 
+(defvar org-persist--index-age nil
+  "The modification time of the index file, when it was loaded.")
+
 (defvar org-persist--report-time 0.5
   "Whether to report read/write time.
 
@@ -589,8 +592,10 @@ COLLECTION is the plist holding data collection."
 (defun org-persist-load:index (container index-file _)
   "Load `org-persist--index' from INDEX-FILE according to CONTAINER."
   (unless org-persist--index
-    (setq org-persist--index (org-persist-read:index container index-file nil))
-    (setq org-persist--index-hash nil)
+    (setq org-persist--index (org-persist-read:index container index-file nil)
+          org-persist--index-hash nil
+          org-persist--index-age (file-attribute-modification-time
+                                  (file-attributes index-file)))
     (if org-persist--index
         (mapc (lambda (collection) (org-persist--add-to-index collection 
'hash)) org-persist--index)
       (setq org-persist--index nil)
@@ -690,17 +695,51 @@ COLLECTION is the plist holding data collection."
         (message "Missing write access rights to org-persist-directory: %S"
                  org-persist-directory))))
   (when (file-exists-p org-persist-directory)
-    (org-persist--write-elisp-file
-     (org-file-name-concat org-persist-directory org-persist-index-file)
-     org-persist--index
-     t t)
-    (org-file-name-concat org-persist-directory org-persist-index-file)))
+    (let ((index-file
+           (org-file-name-concat org-persist-directory 
org-persist-index-file)))
+      (org-persist--merge-index-with-disk)
+      (org-persist--write-elisp-file index-file org-persist--index t t)
+      (setq org-persist--index-age
+            (file-attribute-modification-time (file-attributes index-file)))
+      index-file)))
 
 (defun org-persist--save-index ()
   "Save `org-persist--index'."
   (org-persist-write:index
    `(index ,org-persist--storage-version) nil))
 
+(defun org-persist--merge-index-with-disk ()
+  "Merge `org-persist--index' with the current index file on disk."
+  (let* ((index-file
+          (org-file-name-concat org-persist-directory org-persist-index-file))
+         (disk-index
+          (and (file-exists-p index-file)
+               (org-file-newer-than-p index-file org-persist--index-age)
+               (org-persist-read:index `(index ,org-persist--storage-version) 
index-file nil)))
+         (combined-index
+          (org-persist--merge-index org-persist--index disk-index)))
+    (when disk-index
+      (setq org-persist--index combined-index
+            org-persist--index-age
+            (file-attribute-modification-time (file-attributes index-file))))))
+
+(defun org-persist--merge-index (base other)
+  "Attempt to merge new index items in OTHER into BASE.
+Items with different details are considered too difficult, and skipped."
+  (if other
+      (let ((new (cl-set-difference other base :test #'equal))
+            (base-files (mapcar (lambda (s) (plist-get s :persist-file)) base))
+            (combined (reverse base)))
+        (dolist (item (nreverse new))
+          (unless (or (memq 'index (mapcar #'car (plist-get item :container)))
+                      (not (file-exists-p
+                            (org-file-name-concat org-persist-directory
+                                                  (plist-get item 
:persist-file))))
+                      (member (plist-get item :persist-file) base-files))
+            (push item combined)))
+        (nreverse combined))
+    base))
+
 ;;;; Public API
 
 (cl-defun org-persist-register (container &optional associated &rest misc
@@ -951,6 +990,9 @@ Do nothing in an indirect buffer."
 (defun org-persist-gc ()
   "Remove expired or unregistered containers and orphaned files.
 Also, remove containers associated with non-existing files."
+  (if org-persist--index
+      (org-persist--merge-index-with-disk)
+    (org-persist--load-index))
   (unless (and org-persist-disable-when-emacs-Q
                ;; FIXME: This is relying on undocumented fact that
                ;; Emacs sets `user-init-file' to nil when loaded with