How to merge editing history from one Catalog file to another (same images, but different pathnames)
Greetings. I've been using various photo-editing apps for a long time, but I'm new to Lightroom, and in particular to its catalog-management features. Until very recently, I simply used the regular on-disk structure of filenames and directories to organize my photo collection… and it seems I've run into a problem arising from my incomplete understanding of how Lightroom stores editing data, and as a result I have, at least for the moment, lost numerous hours of editing work. I'm confident the work can be recovered; the question is how. I decided it would be prudent to ask for advice here before improvising a recovery attempt on my own.
Essentially, here's what happened:
(1) Over the past week or two, I've been using Lightroom to edit some of the images that I originally captured over the past seven weeks or so (since 1/1/2020). These images were stored on disk, using a rudimentary directory structure, mostly limited to one directory per shooting date, with no further differentiation inside each directory. I had imported all of those images into Lightroom as a new, separate Catalog designated for the year 2020.
(2) Three days ago, I took a break from photo editing per se, quit the Lightroom application, and went through the on-disk directories where my 2020 images are stored, further organizing them with multiple levels of subdirectories to designate different locations each day, different subjects, image series intended to be combined for HDR and/or panorama purposes, etc. (This was a task I felt I could accomplish more efficiently outside of Lightroom, and I made sure to do it while Lightroom was NOT running, to avoid possible conflicts.)
(3) The next morning, I opened Lightroom, and unsurprisingly, it was befuddled as to the on-disk location of the image files in my Catalog. For the most part, it was only the directory structure I had changed, not the filenames of the individual image files, which made me think Lightroom ought to be able to figure it out on its own, with prompting — but apparently, that's not the case. I could live with hand-holding Lightroom through the process of identifying the new pathname for the previously-existing directories, but that alone would not be sufficient, as I had created a lot of new subdirectories that Lightroom was unaware of. I attempted to use the Sync function to get around that problem, but Lightroom still was going to require me to point-and-click identify the new location of each individual one of roughly a thousand image files, which is something I was unwilling to undertake. The alternative was to use the options to import new images into the catalog, and to delete missing images from the catalog. At this point, I was assuming that all the editing steps for those photos I had already edited were stored in some form either inside the DNG files themselves, or in sidecar files; and based on that assumption, I expected this method would achieve my desired result. So that's what I had Lightroom do.
(4) Everything seemed fine over the past couple of days, as I edited additional photos that I hadn't gotten to before. It was only this morning, when I went to view some of the painstaking edits that I had made _before_ the directory restructuring, that I discovered the problem: The original images are there, but ALL edits I made prior to the re-import have vanished.
Now, fortunately, I have my computer system set up to make hourly and nightly backups, so I'm confident I can recover the Catalog file as it existed immediately prior to my re-import of all the images. I'm assuming now that all my previous edits are contained within that file.
And so, once I have the pre-restructure version of the Catalog (".lrcat") file in hand, in addition to the current version which contains the edits I've made over the past couple of days… what is the optimal procedure to effectively and non-destructively merge the editing history from the older catalog file into the current one?
For the record, I'm using Lightroom Classic v9.2 on macOS Catalina v10.15.3. Thanks in advance for your help!
