bisync: enforce --check-access during --resync

--check-access is now enforced during --resync, preventing data loss in certain user error scenarios
https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=%2D%2Dcheck%2Daccess%20doesn%27t%20always%20fail%20when%20it%20should

cmd/bisync/operations.go

@@ -341,6 +341,38 @@ func (b *bisyncRun) resync(octx, fctx context.Context, listing1, listing2 string
 		return err
 	}
 
+	// Check access health on the Path1 and Path2 filesystems
+	// enforce even though this is --resync
+	if b.opt.CheckAccess {
+		fs.Infof(nil, "Checking access health")
+
+		ds1 := &deltaSet{
+			checkFiles: bilib.Names{},
+		}
+
+		ds2 := &deltaSet{
+			checkFiles: bilib.Names{},
+		}
+
+		for _, file := range filesNow1.list {
+			if filepath.Base(file) == b.opt.CheckFilename {
+				ds1.checkFiles.Add(file)
+			}
+		}
+
+		for _, file := range filesNow2.list {
+			if filepath.Base(file) == b.opt.CheckFilename {
+				ds2.checkFiles.Add(file)
+			}
+		}
+
+		err = b.checkAccess(ds1.checkFiles, ds2.checkFiles)
+		if err != nil {
+			b.critical = true
+			return err
+		}
+	}
+
 	copy2to1 := []string{}
 	for _, file := range filesNow2.list {
 		if !filesNow1.has(file) {

cmd/bisync/testdata/test_check_filename/golden/test.log

@@ -39,10 +39,12 @@ Bisync error: bisync aborted
 (10)  : move-listings path2-missing
 
 (11)  : test 3. put the remote subdir .chk_file back, run resync.
-(12)  : copy-file {path1/}subdir/.chk_file {path2/}
+(12)  : copy-file {path1/}subdir/.chk_file {path2/}subdir/
 (13)  : bisync check-access resync check-filename=.chk_file
 INFO  : Synching Path1 "{path1/}" with Path2 "{path2/}"
 INFO  : Copying unique Path2 files to Path1
+INFO  : Checking access health
+INFO  : Found 2 matching ".chk_file" files on both paths
 INFO  : Resynching Path1 to Path2
 INFO  : Resync updating listings
 INFO  : Bisync successful

cmd/bisync/testdata/test_check_filename/scenario.txt

@@ -20,7 +20,7 @@ bisync check-access check-filename=.chk_file
 move-listings path2-missing
 
 test 3. put the remote subdir .chk_file back, run resync.
-copy-file {path1/}subdir/.chk_file {path2/}
+copy-file {path1/}subdir/.chk_file {path2/}subdir/
 bisync check-access resync check-filename=.chk_file
 
 test 4. run sync with check-access. should pass.

docs/content/bisync.md

@@ -165,13 +165,23 @@ Access check files are an additional safety measure against data loss.
 bisync will ensure it can find matching `RCLONE_TEST` files in the same places
 in the Path1 and Path2 filesystems.
 `RCLONE_TEST` files are not generated automatically.
-For `--check-access`to succeed, you must first either:
-**A)** Place one or more `RCLONE_TEST` files in the Path1 or Path2 filesystem
-and then do either a run without `--check-access` or a [--resync](#resync) to
-set matching files on both filesystems, or
+For `--check-access` to succeed, you must first either:
+**A)** Place one or more `RCLONE_TEST` files in both systems, or
 **B)** Set `--check-filename` to a filename already in use in various locations
-throughout your sync'd fileset.
-Time stamps and file contents are not important, just the names and locations.
+throughout your sync'd fileset. Recommended methods for **A)** include:
+* `rclone touch Path1/RCLONE_TEST` (create a new file)
+* `rclone copyto Path1/RCLONE_TEST Path2/RCLONE_TEST` (copy an existing file)
+* `rclone copy Path1/RCLONE_TEST Path2/RCLONE_TEST  --include "RCLONE_TEST"` (copy multiple files at once, recursively)
+* create the files manually (outside of rclone)
+* run `bisync` once *without* `--check-access` to set matching files on both filesystems
+will also work, but is not preferred, due to potential for user error 
+(you are temporarily disabling the safety feature).
+
+Note that `--check-access` is still enforced on `--resync`, so `bisync --resync --check-access` 
+will not work as a method of initially setting the files (this is to ensure that bisync can't 
+[inadvertently circumvent its own safety switch](https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=3.%20%2D%2Dcheck%2Daccess%20doesn%27t%20always%20fail%20when%20it%20should).)
+
+Time stamps and file contents for `RCLONE_TEST` files are not important, just the names and locations.
 If you have symbolic links in your sync tree it is recommended to place
 `RCLONE_TEST` files in the linked-to directory tree to protect against
 bisync assuming a bunch of deleted files if the linked-to tree should not be
@@ -1108,3 +1118,4 @@ about _Unison_ and synchronization in general.
 ### `v1.64`
 * Fixed an [issue](https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=1.%20Dry%20runs%20are%20not%20completely%20dry) 
 causing dry runs to inadvertently commit filter changes
+* `--check-access` is now enforced during `--resync`, preventing data loss in [certain user error scenarios](https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=%2D%2Dcheck%2Daccess%20doesn%27t%20always%20fail%20when%20it%20should)