chunker: prevent chunk corruption, survive meta-like input

docs/content/chunker.md

@@ -115,11 +115,16 @@ original content.
 When the `list` rclone command scans a directory on wrapped remote,
 the potential chunk files are accounted for, grouped and assembled into
 composite directory entries. Any temporary chunks are hidden.
-`list` can sometimes come across composite files with missing or invalid
-chunks, eg if wrapped file system has been tampered with or damaged.
-If chunker detects a missing chunk it will by default silently ignore
-the whole group. You can use the `--chunker-fail-on-bad-chunks`
-rclone option to make `list` fail with a loud error message.
+
+List and other commands can sometimes come across composite files with
+missing or invalid chunks, eg. shadowed by like-named directory or
+another file. This usually means that wrapped file system has been directly
+tampered with or damaged. If chunker detects a missing chunk it will
+by default print warning, skip the whole incomplete group of chunks but
+proceed with current command.
+You can set the `--chunker-fail-hard` flag to have commands abort with
+error message in such cases.
+
 
 #### Chunk names
 
@@ -368,19 +373,18 @@ Metadata is a small JSON file named after the composite file.
         - Simple JSON supports hash sums and chunk validation.
         - It has the following fields: ver, size, nchunks, md5, sha1.
 
-#### --chunker-fail-on-bad-chunks
+#### --chunker-fail-hard
 
-The list command might encounter files with missinng or invalid chunks.
-This boolean flag tells what rclone should do in such cases.
+Choose how chunker should handle files with missing or invalid chunks.
 
-- Config:      fail_on_bad_chunks
-- Env Var:     RCLONE_CHUNKER_FAIL_ON_BAD_CHUNKS
+- Config:      fail_hard
+- Env Var:     RCLONE_CHUNKER_FAIL_HARD
 - Type:        bool
 - Default:     false
 - Examples:
     - "true"
-        - Fail with error.
+        - Report errors and abort current command.
     - "false"
-        - Silently ignore invalid object.
+        - Warn user, skip incomplete file and proceed.
 
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